sustainability

Article Environmental Comparison of Solutions for Heating and Cooling

Ida Franzén, Linnéa Nedar and Maria Andersson * Division of Energy Systems, Department of Management and Engineering, Linköping University, SE-581 83 Linköping, Sweden; [email protected] (I.F.); [email protected] (L.N.) * Correspondence: [email protected]; Tel.: +46-13 282269

 Received: 31 October 2019; Accepted: 6 December 2019; Published: 10 December 2019 

Abstract: Humanity faces several environmental challenges today. The planet has limited resources, and it is necessary to use these resources effectively. This paper examines the environmental impact of three energy solutions for the heating and cooling of buildings. The solutions are conventional and cooling, a smart energy solution for heating and cooling (ectogrid™), and . The ectogrid™ balances energy flows with higher and lower temperatures to reduce the need for supplied energy. The three solutions have been studied for Medicon Village, which is a district in the city of Lund in Sweden. The study shows that the energy use for the conventional system is 12,250 MWh for one year, and emissions are 590 tons of CO2 equivalents. With ectogrid™, the energy use is reduced by 61%, and the emissions are reduced by 12%, compared to the conventional system. With geothermal energy, the energy use is reduced by 70%, and the emissions by 20%. An analysis is also made in a European context, with heating based on natural gas and cooling based on air conditioners. The study shows that the environmental impact would decrease considerably by replacing the intensive solution with ectogrid™ or geothermal energy.

Keywords: district-heating system; smart energy systems; ectogrid; geothermal energy; ; building energy solutions

1. Introduction The greenhouse gas emissions have led to an ongoing climate change, which can have devastating consequences. A considerable source of these emissions is the extraction and transformation of energy. According to the IPCC (Intergovernmental Panel on Climate Change) [1], a good quarter of the global greenhouse gas emissions come from electricity and heat production. Therefore, it is of paramount importance to reduce the use of electricity and heat and, at the same time, increase the share of . Smarter energy solutions for buildings can be one way of reaching the climate goals. Buildings need heating and cooling systems to ensure a comfortable and functioning indoor-air condition. District heating and cooling are system solutions where heat and cold are distributed to customers through a grid [2]. This technology is common in Swedish cities, but the limited reach of the grid means that buildings situated far from the city centre cannot be connected. A thorough environmental evaluation is necessary to make a well-founded decision about which energy solution is the most beneficial. An environmental evaluation assesses the performance of the energy solution in relation to the energy and climate targets [3,4]. The evaluation gives the opportunity to choose the energy solution that will have a low climate impact in the longer time perspective, that is, a solution in line with the determined environmental goals nationally as well as internationally. ectogrid™ [5] is one of the approaches to a smart energy solution since ectogrid™ can improve the energy performance of the buildings. ectogrid™ is based on already existing technology for heat pumps, cooling machines, and energy distribution grids, but in a new combination and with new

Sustainability 2019, 11, 7051; doi:10.3390/su11247051 www.mdpi.com/journal/sustainability Sustainability 2019, 11, 7051 2 of 17 features [6]. The aim of ectogrid™ is to make use of energy that is currently being wasted, thus reducing the demand for additional heat and cold sources [7]. This is achieved through the ability of the heat pumps to transfer the energy, i.e., to allow heat that has been generated from buildings that need cooling to be used in buildings that need heating and vice versa. The buildings are connected via a network with water, which is used as an external heat source. The aim of this paper is to evaluate the environmental impact of a new energy solution for heating and cooling that is called ectogridTM. ectogridTM will be compared with two existing technologies, which are conventional district heating and cooling and geothermal energy. The purpose is also to ensure that this study can contribute to an improved understanding of how different energy solutions could interact with each other in the future. The objectives of the study will be achieved through a case study with three energy solutions for heating and cooling in the area of Medicon Village in Lund, Sweden. The studied solutions include conventional district heating and cooling (Case 1), ectogrid™ (Case 2), and geothermal energy (Case 3). The following aspects are covered in this studied; 1) the energy use, divided by energy carrier, for the three energy solutions; 2) the energy solution that gives the least environmental impact in the case of Medicon Village. The study is based on data for Medicon Village collected in 2015. Economic aspects will not be explored in this paper. Some economic aspects of introducing ectogridTM in Germany and the United Kingdom have been studied in [8].

2. Heating and Cooling Buildings

2.1. Conventional Approaches The principle for both heat pumps and cooling machines is the same. By using additional work to aid the process in the form of electricity, heat can be transferred from an environment of lower temperature to an environment of higher temperature [9]. The machines are often optimized depending on whether a cooling or heating demand shall be fulfilled. The highest efficiency is achieved when there is a demand for both the heat from the condenser and the cold from the evaporator. Machines made to easily shift between fulfilling a heating and a cooling demand are called refrigeration heat pumps [10]. One way of determining how efficiently a heat pump or cooling machine can transform electric power into heating or cooling power is through the coefficient of performance, COP. In a heat pump, the COP for heating is calculated as the ratio between delivered heat power and added electric power, as shown in Equation (1) [10]: P f + Pk COPheating = , (1) Pk where Pf is the heat absorbed at the evaporator, and Pk is electricity added to the compressor. In a cooling machine, COP for cooling is calculated according to Equation (2) [10]:

P f COPcooling = . (2) Pk

The higher the COP, the more efficient the machine. The COP largely depends on the working temperatures of the machine; the smaller the difference between evaporator and condenser, the higher the COP [9]. Heat pump solutions are getting more and more efficient. Heat pump manufacturers strive to maximize energy efficiency. One way to do so is to provide multiple services by one single unit, for example, to heat water by using residual energy from cooling the building. In this way, even a heating demand is fulfilled without adding external energy [11]. Closed water-loop heat pump systems are used for achieving this. Energy from condensation is transferred through a water loop and given to the evaporation of reversible heat pumps, thus reducing the energy needed to fulfil simultaneous heating and cooling demands in the building [12]. This makes heat pumps an energy-efficient solution in applications where there are different energy needs [11]. Sustainability 2019, 11, 7051 3 of 17

Geothermal heat, which is stored in the bedrock, originates from pressure and nuclear reactions at the core of the earth [13]. In a borehole solution, heating and cooling from the rock is utilized in a waterborne system running through several holes that are drilled in the rock [14]. A heat pump or a cooling machine can be used to increase or decrease the temperature level of the extracted energy. The temperature in the boreholes is lowered when the heat is extracted. The size of the temperature drop depends on the heating load, the depth of the boreholes, and the properties of the rock [14]. This can be used for seasonal storage of heat and cold. The temperature in the boreholes is lowered in the winter due to the heat extraction and because of the thermal inertia of the rock. The temperature is still low when summer arrives [15]. The cold borehole storage can be used to cool buildings, whereby heat is restored to the boreholes before the winter. A seasonal storage does not reduce the energy use of the building, but it replaces purchased energy with local geothermal energy [15]. A geothermal energy solution has high investment costs but low running costs and is suitable for buildings with both a heating and a cooling demand [16]. Local geological conditions determine how much power and energy that can be extracted from the boreholes and, thus, the dimension of the system [14]. A district heating system is aimed at making use of resources that would otherwise go to waste. The source of the heat is usually upgraded excess heat from combined heat and power plants or industrial companies. The heat is brought to the customers through a distribution grid with hot water. The size of the grid is limited by losses in the pipes and the density of customers in the area, where customer density needs to be high enough to warrant an efficient system [10]. A certain pressure is necessary to deliver the heat to all customers in the grid [2]. The most common technology today is often referred to as the third-generation district heating and was developed in the 1970s. The supply-side temperature lies between 80 ◦C and 100 ◦C and the return temperature lies between 40 ◦C and 50 ◦C[17]. The fourth-generation district heating is currently being developed and is characterized by a lower supply-side temperature with a maximum of 70 ◦C[18] and a minimum of 50 ◦C. This makes it possible to reduce the grid losses and incorporate sources of low-temperature and renewable energy. The principles of are basically the same as for district heating. Water is cooled centrally and distributed through pipes to buildings that need cooling [2]. Because of the low temperatures of the system, a larger mass flow of the water is needed to deliver the same amount of energy, compared to district heating [2].

2.2. ectogridTM The smart energy solution that is described by ectogrid™ [3] is a bidirectional low-temperature district heating system [19]. It was invented by Ph.D. Per Rosén [3]. ectogrid™ consists of the following fundamental parts:

Grid of pipes connecting the buildings and the components. • Components in the buildings, mainly heat pumps and cooling machines. • A passive balancing unit, i.e., a hot water storage tank that evens out daily demand variations. • An active balancing unit, i.e., an external source of energy, such as a reversible heat pump, • district heating or cooling, or geothermal energy.

The buildings have different equipment since their heating and cooling demands are different. A heat pump or cooling machine is the most crucial part of the system. The heat pump uses the warm side of the grid to add heat until the heating demand is met. Similarly, if the building has a cooling demand, the cooling machine uses the cold side of the grid to add cold until the cooling demand is met. The energy transformation becomes more efficient in this way since the temperature interval of the grid suits the heat pumps and cooling machines better compared to using the outside air. Figure1 shows the components of ectogrid ™. The system consists of a network of pipes with water that transports the heat and the cold between the buildings. This is the same idea as with district heating and cooling. However, where district heating and cooling require four pipes, ectogrid™ uses Sustainability 2019, 11, 7051 4 of 17 Sustainability 2019, 11, x FOR PEER REVIEW 4 of 17

only two. Instead of having one feeding pipe and one return pipe for heating as well as for cooling, ectogrid™there is only uses a hotonly and two. a coldInstead pipe. of Thishaving is called one feedi theng hot pipe and and the coldone return side. pipe for heating as well as for cooling, there is only a hot and a cold pipe. This is called the hot and the cold side.

FigureFigure 1. 1. AnAn example example of of a a possible possible combination combination of of demands demands and and components components in in ectogrid ectogridTMTM. .

WithWith ectogrid™, ectogrid™ ,every every building building can can take take or or give give en energyergy to to the the grid grid to to fulfil fulfil its its heating heating or or cooling cooling demand,demand, meaning meaning that there isis nono predeterminedpredetermined direction direction of of the the flow flow in thein the pipes. pipes. If demand If demand for heatfor heatdominates dominates in many in many buildings, buildings, cooled cooled water iswater pushed is towardspushed thetowards cold pipe,the cold thus pipe, moving thus towards moving the towardsthermal the storage thermal tank. storage If demand tank. wereIf demand to change were so to that change the demandso that the for demand cold is higher, for cold water is higher, in the watercold pipein the would cold pipe move would towards move the towards buildings. the This buil alsodings. means This thatalso themeans temperature that the temperature of the water of in thethe water pipes in will the not pipes be constant,will not be but constant, instead but vary inst withinead vary certain within intervals; certain hence intervals; the namehence ectogridthe name™ , ectogrid™,i.e., an ectothermic i.e., an ectothermicsystem. Daily system. variations Daily invariat heatingions andin heating cooling and demand cooling are demand controlled are by controlled a thermal bystorage a thermal tank storage connected tank to connected the grid. to Depending the grid. Depending on how much on how hot andmuch cold hot water and cold that water is sent that to theis senttank, to the the temperature tank, the temperature in the tank in will the vary tank between will vary an between upper and an upper a lower and limit. a lower When limit. the lowerWhen limitthe loweris reached, limit is heat reached, must beheat added must to be the added system. to the When system. the upper When limit the upper is reached, limit heatis reached, must be heat removed. must beThis removed. is done This by the is activedone by balancing the active unit, balancing which can unit, have which several can solutions.have several The solutions. active balancing The active unit balancingcould be aunit hybrid could net be connected a hybrid net to districtconnected heating, to district district heating, cooling, district or a gascooling, boiler. or Ita couldgas boiler. also beIt coulda standalone also be a system standalone with geothermalsystem with energy geothermal or reversible energy or air-source reversible heat air-source pumps. heat pumps. ectogrid™ectogrid™ isis a alow-temperature low-temperature system system with with temp temperatureseratures ranging ranging between between 16 °C 16 and◦C and 40 °C 40 on◦C theon hot the side hot sideand andbetween between 6 °C6 and◦C and30 °C 30 on◦C the on cold the coldside. side. The temperature The temperature difference difference between between the sidesthe sides is set is to set 10 to °C. 10 The◦C. pipes The pipes are not are insulated not insulated and can, and can,therefore, therefore, take takeup or up release or release energy energy to the to surroundingthe surrounding ground. ground. The Thesystem system uses uses small small circul circulationation pumps, pumps, which which consider consider that that there there is is no no predefinedpredefined direction direction of of the the flow flow in in the the system. system. This This means means that that exactly exactly the the necessary necessary flow flow is is created created andand losses losses through through choking choking are are minimized. minimized. In In the the ec ectogridtogrid™™ system,system, the the energy energy is is balanced balanced internally internally withinwithin the building,building, betweenbetween buildings buildings in in the the system, system, and and in the in thermalthe thermal storage storage tank. Balancingtank. Balancing means meansthat the that system the system utilizes utilizes the heat the pumps heat topumps provide to multipleprovide servicesmultiple to services both fulfil to both a heating fulfil and a heating cooling anddemand cooling at the demand same time. at the The same balancing time. isThe made balanc internallying is within made theinternally connected within buildings the connected when there buildingsis a simultaneous when there heating is a simultaneous and cooling heating demand. and In cooling those cases, demand. the In energy those addedcases, the to and energy subtracted added tofrom and the subtracted grid is cancelled from the out. grid When is cancelled there is anout. overall When dominating there is an heating overall or dominating cooling demand heating in theor coolingsystem, demand energy isin neededthe system, from energy the thermal is needed storage from tank. the thermal If a dominant storage demand tank. If justa dominant lasts for demand a shorter justperiod, laststhe for variationsa shorter period, are balanced the variations within the are tank, balanced and no within external the energytank, and is needed. no external energy is needed.

2.3. Perspectives on Energy Solutions Sustainability 2019, 11, 7051 5 of 17

2.3. Perspectives on Energy Solutions There are arguments both in favour of and against heat pumps and district heating from an energy efficiency perspective. Electricity is characterized by high exergy, meaning that most of the energy is used for the desired purpose, resulting in low losses and high energy efficiency [2]. Losses occur when electrical energy is transformed into thermal energy, which is an energy form characterized by low exergy. Heat pumps use electricity to create heat, which can be questioned, as the energy resources are not used in the most efficient way [20]. From an exergy point of view, district heating is an energy-efficient solution since heat is used for heating. In the third-generation district heating, the temperatures and pressure need to be adjusted to deliver the right temperature to the customer at the end of the system. With the fourth-generation district heating, the development is moving towards lower temperatures. The limitations of the fourth generation are that it is mainly suitable for new or renovated buildings with similar demands and that it has low compatibility with district cooling [21]. Ultra-low temperature district heating uses distributed heat pumps to fulfil heating demands, thus making it easier to adapt to buildings with varying demand. Cold district heating uses distributed heat pumps and cooling machines together with a waterborne grid to fulfil both heating and cooling demands. For heat pumps, the development is moving towards using the ability of heat pumps to produce heating and cooling at the same time in order to increase the efficiency [11]. The development in the different areas coincide in ectogrid™, which is sometimes called the fifth-generation district heating [2]. Using a bidirectional low-temperature network and balancing heating and cooling demand on a district level takes advantage of the development in the different areas.

2.4. Environmental Impact It is not always easy to instantly and intuitively understand which alternative is the best for the environment. Therefore, methods for quantifying environmental impact are essential. Usually, there is no fully objective way to measure; instead, the results depend on the perspective, system boundaries, and allocation methods used. The perspective that is adopted also influences whether marginal or average values are used in calculations of environmental impact. This greatly affects the results of the evaluation. Marginal electricity values are based on the electricity produced in the plant with the highest running cost. This plant is the last to be started and the first to be turned off. Average electricity values are based on an average of the electricity production during a historical period. Similarly, there are also marginal and average values for district heating. In the Nordic electricity mix, the marginal production is often considered to be Danish coal condensing power, but in reality, the marginal production varies during the year [22]. The emission factor can differ up to 100 times between different kinds of electricity production; thus, the choice of factor for electricity has a large influence on the results of an environmental evaluation [4]. The factor that is selected depends on the perspective used, as well as what those performing the environmental evaluation want to present [22]. In Sweden, a certificate of origin is given for electricity produced from renewable sources. This certificate can be traded to assure that the purchased electricity comes from a renewable source [23]. When performing an environmental evaluation using historical data, both [23] and the Heating Market Committee [3] recommend using the Nordic countries, excluding Iceland, as the limitation of the electric system. The electricity grid in these countries is connected, and there is a common electricity market, Nord Pool. The Swedish Energy Market Inspectorate reports the CO2 emissions for Nordic residual electricity each year. The residual electricity mix represents the electricity that remains when electricity that is marked as renewable has been subtracted. This is the electricity that customers receive if they do not make an active choice of electricity production source. Since the residual mix has a lower share of renewable energy, it usually has a lower environmental performance than the total electricity production [23]. The environmental impact cannot be evaluated fully through one indicator alone, but one fundamental factor is climate impact. Both the Heating Market Committee [3] and [24] Sustainability 2019, 11, x FOR PEER REVIEW 6 of 17 Sustainability 2019, 11, 7051 6 of 17

Marketemphasize Committee climate impact[3] and as [24] the emphasize most important climate parameter impact ofas anthe environmental most important evaluation. parameter Climate of an environmentalimpact is calculated evaluation. using factors Climate derived impact from is life-cycle calculated assessments. using factors Emission derived factors from can be life-cycle found at assessments.different levels Emission of detail, factors ranging can from be found a specific at different green-house levels gas of detail, emitted ranging from the from burning a specific of a green- certain housefuel to gas CO 2emittedequivalents from per the energy burning carrier of a orcertain per district fuel to heating CO2 equivalents grid. This informationper energy carrier together, or withper districtthe energy heating use of grid. a specific This customerinformation (e.g., together, representing with athe building), energy givesuse of the a climatespecific impact customer caused (e.g., by representingthat customer. a building), gives the climate impact caused by that customer.

3.3. Case Case Studies Studies MediconMedicon Village isis aa science science park park situated situated in in Lund Lund in Sweden.in Sweden. In MediconIn Medicon Village, Village, there there are more are morethan 1600than people1600 people working working at more at than more 120 than different 120 organisationsdifferent organisations and companies and companies with businesses with businessesin medical in science medical and science life science and life [25]]. science The properties [25]]. The coverproperties an area cover of 80,000 an area m 2of[25 80,000]. The m current2 [25]. Theenergy current solution energy in Mediconsolution in Village Medicon is district Village heating is district and heating district and cooling, district with cooling, an annual with demandan annual of demand10 GWh heatof 10 andGWh 4 GWhheat and cooling 4 GWh [25 ].cooling ectogrid [25].™ hasectogrid™ been implemented has been implemented for the first for time the in first Medicon time inVillage Medicon as a Village pilot project as a pilot and project is expected and is toexpected be finalized to be finalized during 2020 during [25 ].2020 Fifteen [25]. buildingsFifteen buildings will be willconnected, be connected, but the but buildings the buildings will be connectedwill be connected to the district to the heatingdistrict heating and cooling and systemcooling insystem Lund in as Lunda backup as a. backup. Every building Every building will be equippedwill be equipp withed a heat with pump a heat and pump a cooling and a cooling machine, machine, which willwhich be willdimensioned be dimensioned for 50% for of 50% the powerof the power demand. demand. This means This means that 90% that of 90% the of heat the demand heat demand and 85% and of 85% the ofcooling the cooling demand demand will be will covered, be covered, based onbased data on from data the from hourly the measuredhourly measured energy use energy in Medicon use in MediconVillage during Village 2015. during The 2015. remaining The remaining demand willdemand be covered will be bycovered district by heating districtand heating cooling. and cooling. Figure2 Figureshows 2 the shows components the components of ectogrid of ™ectogrid™in Medicon in Medicon Village. Village.

Figure 2. ectogridTM inin Medicon Medicon Village. Village.

TheThe ectogrid™ ectogrid™ system in Medicon Village will contain 400 m3 water divided on 250 m 3 inin the the pipespipes and and 150 m 33 inin the the tank. tank. The The pipes pipes will will be be made made of of polyethylene, polyethylene, and and the the size size of of the the diameter will be be different different for different different buildings, depending on the energy demand of the building. The The active active balancingbalancing unit unit will will consist consist of a reversible heat pump. InIn this this study, study, environmental environmental evaluations are are done done for for three three energy energy system system solutions solutions in in Medicon Medicon Village.Village. In In Case Case 1, 1, the the energy energy use use and and environm environmentalental impact impact are are calculated for for the conventional districtdistrict heating heating and and district district cooling. cooling. This This is is the the current current energy energy solution solution in in Medicon Medicon Village. Village. In In Case Case 2, 2, thethe energy energy use and environmental im impactpact are calculated for an ectogrid™ ectogrid™ system. Case Case 3 3 is is a a fictive fictive casecase to to evaluate evaluate the the option option of of using using heat heat pumps pumps and and cooling cooling machines. machines. To To use use geothermal geothermal energy energy as as thethe energy energy source source for for the heat pumps is, in this case, the most reliable assumption [[26].26]. Sustainability 2019, 11, 7051 7 of 17

4. Method

4.1. Calculations of Energy Use The calculations are made hourly and divided into district heating use and electricity use for each of the three cases. The aim of the calculations is to obtain the sufficient amount of energy needed to meet the heating demand of 10 GWh and the cooling demand of 4 GWh [25]. The method considers the different components of the different energy solutions, including their energy losses. The calculations are performed with a method based on Microsoft Excel [27]. Some assumptions have been made for the calculations. The first assumption is that the internal system components for heating and cooling use the same amount of energy for all the different systems. That makes it possible to neglect the energy use of the components in the calculation. Another assumption is that the energy use for some distribution and circulation pumps are neglected. Only the pumps that will distribute energy between the energy source and the buildings are included in the calculations. In Case 1 and this particular network, the energy supplied to the pump is assumed to be 1.5% of the total energy use [28]. In that case, the pumps are used to deliver the district heating and cooling from the production place. In Case 2 and Case 3, the energy supplied to the pump is estimated to be 1.0% of the total energy use [28]. There are several reasons why the supplied energy to the pump is estimated to be lower in Case 2 and Case 3. In Case 1, higher pressure and more energy are needed to ensure the desired flow to all the customers in the network. In Case 2 and Case 3, the energy source is closer to Medicon Village. The pumps are situated in connection with the components in the system and only use the amount of energy needed to deliver the desired flow. All pumps are assumed to work all the year with the same load. The effects of the position of the polyethylene pipes used in the ectogrid™ system are neglected in the calculations. It is assumed that the distance between the pipes and the distance between the air and the pipes will not affect the heat transfer to and from the pipes. When using electricity in electrical components, the electrical energy will be converted into heat, as said in the second law of thermodynamics [29]. In this study, it is assumed that all heat is utilized in the system.

4.1.1. Case 1—Electricity and Heat Use In Case 1, the use of electricity and heat connected to the district heating and cooling in Medicon Village has been calculated. The aim of the calculations is to find the amount of energy that can meet the heating and cooling demand of 10 GWh and 4 GWh, respectively. Hourly values for the district heating have been calculated in relation to:

Heat demand • System losses • District cooling production • Distribution pumps • District cooling pumps • Hourly values for the electricity have been calculated in relation to:

District cooling production • District cooling pumps • District heating pumps • Energy losses • Heat generated by the district cooling pumps • Hourly values of the heat demand for the different buildings in Medicon Village are used to estimate the total district heating demand. The system losses, as a result of the transmission losses from the pipes, are estimated to 10% of the delivered district heating [2,28]. The use of district cooling for the Sustainability 2019, 11, 7051 8 of 17 different buildings in Medicon Village is calculated in the same way as for the use of district heating. System losses are estimated to 5% [28] of the delivered district cooling. The losses are caused by heat transmission from the surrounding ground and the circulation pumps. The electrical energy demand for the pump needed to obtain the water pressure in the pipes is set to 1.5% of the delivered district cooling [28]. The district cooling is produced by reversible heat pumps. The heat pumps have a COP value of 3 [28], which is used to determine the electricity use of the pumps. The COP value is assumed to be constant over the year. The production of district cooling generates the same amount of heat. This heat has a temperature of about 70–80 ◦C and can be used for district heating [28]. The heat generated from the total district cooling production corresponds to 5.6% of the total district heating production. The same portion of the district cooling allocated to Medicon Village is, therefore, estimated to be available as district heating.

4.1.2. Case 2—Electricity and Heat Use In Case 2, the use of electricity and heat for the ectogrid™ system in Medicon Village is calculated. As in Case 1, the aim of the calculations is to meet the heating and cooling demand of 10 GWh and 4 GWh, respectively. Hourly values have been calculated and divided into district heating in relation to:

Heat demand • System losses • District cooling production • Distribution pumps • District cooling pumps • Hourly values have also been calculated as electricity use or savings in relation to:

Internal balancing • Remaining energy demand • Active balancing unit • Circulations pump • Energy transmissions to the ground • District cooling production • District cooling pumps • District heating pumps • Energy losses • Heat generated by the district cooling pumps • In the model, the heat and cooling demand for Medicon Village during 2015 [25] is used as the starting point for the calculations. From the diagrams of the power demand of the buildings, the sizes of the heat pumps and the cooling machines have been decided from an economic perspective. District heating and district cooling cover the rest of the demand. Hourly values of the electricity needed for the heat pumps and the cooling machines have been calculated by the COP value. The COP value changes depending on the working temperatures for the unit. Data sheets from the suppliers have been used to find how the COP value correlates to the temperature at the supply temperature in the radiator system. The energy supplied to or removed from the thermal storage tank (∆Q) causes a temperature change (∆T) within the tank. The change is calculated with Equation (3) [29], where m is the mass, and c is the specific heat capacity: ∆Q = m c ∆T. (3) ∗ ∗ In the ectogrid™ system in Medicon Village, the temperature difference is set to 10 ◦C between the hot and cold side and is used to calculate a corresponding energy flow concerning the tank [30]. Sustainability 2019, 11, 7051 9 of 17

The active balancing unit is activated when the temperature in the tank reaches the maximum or minimum value. The electricity needed to the tank depends on the energy demand and the COP value of the units in the system. The COP value of the tank has been decided in the same way as for the heat pumps and the cooling machines. Since ectogrid™ is built with non-insulated pipes, there is an energy transmission Q between the pipes and the ground. The energy transmission can be controlled based on the temperature chosen for the ectogrid™, i.e., Tnet. Equations (4)–(6) [31] have been used to calculate the transmissions from the system, where U is the heat-transfer coefficient, and Ay is the outer area of the pipe. The other parameters that have been used are explained in Table1.   Q = UAy Tnet T , (4) − ground

Ry 1 Ryln R = i (5) U k 2 Ay = 2πRyL + 2πRy (6)

Table 1. Parameters for the calculation of the energy transmission from ectogridTM.

Parameter Explanation Value

Ri Inner diameter of the pipe (m) 0.090 Ry Outer diameter of the pipe (m) [32] 0.103 L Length of the pipe (m) 5000 k Thermal conductivity (W/mK) [33] 0.465

Values for Tground for the summer and the winter have been obtained from simulations of district heating systems in the area around Malmö [17]. The values that have been used in this study are Tground = 8 ◦C for the summer and Tground = 3 ◦C for the winter. To calculate the total heat transmissions from the ectogrid™ system, the problem has been divided into two scenarios, one when the heat transfer is favourable for the system, and another when the heat transfer is unfavourable for the system. The heat transfer during the summer is favourable since there is a heat overload in the system. In that case, the heat transfer has been calculated for 40 ◦C on the warm side and 30 ◦C on the cold side. The transferred energy that is favourable has been calculated for the hours during the year when the temperature in the tank is 40 ◦C. When energy is transferred to the ground, less electrical energy is needed to the balancing unit. The heat transfer during the winter is unfavourable for the system when there is a heat demand within the system. In that case, the heat transfer has been calculated for 16 ◦C on the warm side and 8 ◦C on the cold side. The transferred energy that is unfavourable has been calculated for the hours during the year when the temperature in the tank is 6 ◦C. When energy is transferred to the ground, in this case, more electrical energy is needed for the balancing unit. The heat transfer is assumed to be negligible during the hours when the tank neither has the maximum temperature or the minimum temperature. The electrical energy used or saved as a result of the influence of the ground has been calculated as depending on the COP value of the balancing unit.

4.1.3. Case 3—Electricity and Heat Use In Case 3, the electricity use connected to a geothermal energy solution in Medicon Village is calculated, with the aim of meeting the heating and cooling demand of 10 GWh and 4 GWh, respectively. This energy solution is constructed together with E.ON [26]. Hourly values have been calculated and summarized as electricity use in relation to:

Heat pumps for heat production • Sustainability 2019, 11, 7051 10 of 17

Heat pumps for cooling production • Circulation pump • Cooling machines • Coolers • The heat pumps have been dimensioned, as in Case 2, for 50% of the maximum heat power demand, and the rest of the heat demand is covered by electricity. The cooling machines have been dimensioned for the total heat power demand. The total cooling power demand needs to be fulfilled by cooling machines during the periods when no free cooling is available. The hourly electricity use of the heat pumps is calculated from the dimensioned power of the heat pumps and the COP value. The cooler has the same purpose as the active balancing unit during the summer, and because of that, the electricity use is assumed to be the same. The COP value has been calculated in the same way as for the other cases, but, in this case, the evaporating temperature is represented by the geothermal temperature. The geothermal energy is affected by the delivered energy to the buildings, which varies depending on the heat and cooling demand. The geothermal temperature has been set to 4 ◦C from January to March and October to December. For April to June, the temperature has been set to 10 ◦C, and for July to August, the temperature has been set to 15 ◦C. These temperatures represent the average geothermal temperature for these months. Information about the COP value for different evaporating temperatures has been given by [34]. The cooling demand is covered most of the year by free cooling, which, in the calculations, represents a COP value of 30. The cooling machines are necessary to use when the geothermal temperature has increased above 12–13 ◦C and do not have any cooling potential. In the calculations, it is assumed that there is no free cooling potential from July to August. During these months, a COP value of 4 is used.

4.2. Quantification of the Environmental Impact Climate impact is calculated using factors derived from various life-cycle assessments. These factors can be found at different levels of detail, ranging from a specific green-house gas emitted from the burning of a certain fuel to CO2 equivalents per energy carrier or per district heating grid. The Nordic electricity mix gives a value of the climate impact that is not affected by the electricity sale and just the production [35]. This value has been used in this study because it takes into account the emissions of the total electricity production. The emission factor concerning the district heating is declared by Kraftringen [36] every year. The climate impact is formulated as CO2 equivalents per kilowatt hour used by ectogrid™, which includes methane, nitrous oxide, and carbon dioxide. This information multiplied by the amount of energy used gives the climate impact caused by each case. The emission factors are shown in Table2.

Table 2. Emission factors for electricity and district heating.

Emission Factor Energy Carrier (g CO2 equivalents/kWh) District heating, Lund [37] 31.0 Nordic electricity production mix [35] 131.2

5. Results

5.1. Energy Use for the Different Cases Figure3 shows the annual energy use for Case 1, Case 2, and Case 3. The energy use has been calculated according to the procedures described in Section4, including 4.1.1, 4.1.2, and 4.1.3. The calculations show that the energy use of Case 1 amounts to 12,250 MWh, which is the highest of the three cases. The electricity use for Case 1 is, however, the lowest. The energy use of Case 2 Sustainability 2019, 11, 7051 11 of 17

Sustainability 2019, 11, x FOR PEER REVIEW 11 of 17 is considerably lower and represents a reduction of 61% compared to Case 1. The energy use for Case 3 is reduced further and represents a reduction of 70%. The results for Case 1 and Case 2 can Sustainability 2019, 11, x FOR PEER REVIEW 11 of 17 be verified by [25], where approximately the same energy amounts are obtained for the conventional district heating and cooling system and ectogridTM and, also, a similar relative difference in energy use between the two cases.

Figure 3. Energy use for one year for all the cases, divided on district heating (blue) and electricity

Figure(red). 3. Energy use for one year for all the cases, divided on district heating (blue) and electricity (red). Figure 3. Energy use for one year for all the cases, divided on district heating (blue) and electricity FigureFigure4 shows4 shows the the climate climate impact impact quantifiedquantified inin thethe number of of CO CO2 equivalentsequivalents for for a year. a year. The (red). 2 Theprocedure procedure forfor the the calculations calculations is isexplained explained in in4.2, 4.2, and and the the emission emission factors factors forfor the the electricity electricity and anddistrict district heating heating are are shown shown in in Table Table 2.2. Case 1 hashas thethe highesthighest emissions emissions with with 590 590 tons tons of of CO CO2 Figure 4 shows the climate impact quantified in the number of CO2 equivalents for a year. The2 equivalents.equivalents.procedure Casefor Case the 2 reduces2 calculationsreduces the the CO COis2 explainedequivalents2 equivalents in by 4.2,by 12% 12% and compared comparedthe emission to to Case Case factors 1, 1, and and for Case Casethe3 electricity reduces3 reduces the andthe COCOequivalents2 equivalents by by 20%. 20%. The The percentage percentage reduction reduction in in emissions emissions for for Case Case 2 2 and and Case Case 3, 3, compared compared to to district2 heating are shown in Table 2. Case 1 has the highest emissions with 590 tons of CO2 CaseCase 1, 1, is is less less than than the the corresponding corresponding percentage percentage reduction reduction in in energy energy use use (see (see Figure Figure3). 3). equivalents. Case 2 reduces the CO2 equivalents by 12% compared to Case 1, and Case 3 reduces the CO2 equivalents by 20%. The percentage reduction in emissions for Case 2 and Case 3, compared to Case 1, is less than the corresponding percentage reduction in energy use (see Figure 3).

Figure 4. Emissions of CO equivalents for one year for all three cases. Figure 4. Emissions of CO2 2 equivalents for one year for all three cases. 5.2. Environmental Evaluation for Higher Emission Factors 5.2. Environmental Evaluation for Higher Emission Factors This section showsFigure how 4. Emissions the choice of ofCO emission2 equivalents factors for one for year Sweden for all three affects cases. the environmental This section shows how the choice of emission factors for Sweden affects the environmental evaluation. It also investigated how the environmental impact would change if ectogrid™ replaces evaluation.5.2. Environmental It also investigated Evaluation for how Higher the Emissionenvironmen Factorstal impact would change if ectogrid™ replaces a a common energy solution in a country on the European continent. commonThis energy section solution shows inhow a country the choice on theof emissionEuropean factors continent. for Sweden affects the environmental evaluation. It also investigated how the environmental impact would change if ectogrid™ replaces a 5.2.1. District Heating common energy solution in a country on the European continent. In Lund, most of the district heating is produced by biofuels, and 5% is produced by fossil fuels. Malmö,5.2.1. District a city Heatingsituated 20 km southwest of Lund, uses more fossil fuels, natural gas, and waste to produceIn Lund, their mostdistrict of heating.the district This heating leads isto produced a higher emissionby biofuels, factor and in5% Malmö is produced than inby Lund. fossil fuels.It is, Malmö, a city situated 20 km southwest of Lund, uses more fossil fuels, natural gas, and waste to produce their district heating. This leads to a higher emission factor in Malmö than in Lund. It is, Sustainability 2019, 11, 7051 12 of 17

5.2.1. District Heating In Lund, most of the district heating is produced by biofuels, and 5% is produced by fossil fuels.

Malmö,Sustainability a city 2019 situated, 11, x FOR 20 PEER km southwestREVIEW of Lund, uses more fossil fuels, natural gas, and waste 12 to of 17 produce their district heating. This leads to a higher emission factor in Malmö than in Lund. It is, therefore, interesting to compare the climate impact for Medicon Village in the district-heating system oftherefore, Lund with interesting a Medicon to Village compare that the would climate be situated impact for in the Medicon district-heating Village in system the district-heating of Malmö. Table system3 presentsof Lund the with emission a Medicon factors Village for the that two would district be heatingsituatedsystems. in the district-heating system of Malmö. Table 3 presents the emission factors for the two district heating systems. Table 3. Emission factors for the district heating systems in Lund and Malmö [37].

Table 3. Emission factors for the district heating systemsEmission in Lund Factor and Malmö [37]. District Heating System (g CO2 equivalents/kWh) Emission Factor DistrictLund Heating System 31.0 (g CO2 equivalents/kWh) Malmö 127.0 Lund 31.0 Malmö 127.0 FigureFigure5 shows 5 shows the the climate climate impact impact for for Medicon Medicon Village Village in thein the district-heating district-heating systems systems of Lundof Lund andand Malmö. Malmö. The The electricity electricity isis stillstill calculated as Nord Nordicic electricity electricity mix. mix. The The result result shows shows that that for forCase Case1, the 1, the emissions emissions areare much much higher higher when when the the district heating isis delivereddeliveredfrom from Malmö Malmö (red (red bar), bar), TM comparedcompared to Lundto Lund (blue (blue bar) bar) because because of theof the higher higher emission emission factor factor for for Malmö. Malmö. If ectogridIf ectogridTMis is introducedintroduced in in Malmö, Malmö, the the red red bar bar for for Case Case 2, the2, the emissions emissions are are reduced reduced by by 61% 61% compared compared to Caseto Case 1. 1.

Figure 5. Emissions for one year for Case 1 and Case 2 in Lund (blue) and Malmö (red). Figure 5. Emissions for one year for Case 1 and Case 2 in Lund (blue) and Malmö (red). 5.2.2. Electricity 5.2.2. Electricity As mentioned in Section 2.4, the climate impact for the electricity can be evaluated in different ways dependingAs mentioned on the in choice section of 2.4, perspective the climate for impact allocating for emissions.the electricity The can three be perspectives evaluated in selected different forways this studydepending are Nordic on the residualchoice of electricity, perspective Nordic for allocating electricity emissions. mix, and The wind three power. perspectives The emission selected factorsfor this for study the three are Nordic perspectives residual are electricity, shown in TableNordic4. electricity The factors mix, depend and wind on the power. amount The of emission fossil fuelsfactors that for are the allocated three toperspectives the electricity are production.shown in Table 4. The factors depend on the amount of fossil fuels that are allocated to the electricity production. Table 4. Emission factors for different scenarios. Table 4. Emission factors for different scenarios. Emission Factor Scenario (g COEmission2 equivalents Factor/kWh) Scenario Nordic residual electricity [38](g CO2 equivalents/kWh) 336.4 NordicNordic electricity residual mix electricity [35] [38] 131.2336.4 WindNordic power electricity [24] mix [35] 131.2 15.2 Wind power [24] 15.2 The results in Figure 6 show that Case 1 has the lowest impact when the emissions from the electricity production are high (i.e., the emission factors for the Nordic residual electricity). When the emissions from the electricity production are lower (i.e., the emission factors for the Nordic electricity mix and wind power), Case 2 and Case 3 are more favourable. Sustainability 2019, 11, 7051 13 of 17

The results in Figure6 show that Case 1 has the lowest impact when the emissions from the electricity production are high (i.e., the emission factors for the Nordic residual electricity). When the Sustainability 2019, 11, x FOR PEER REVIEW 13 of 17 emissions from the electricity production are lower (i.e., the emission factors for the Nordic electricity mix and wind power), Case 2 and Case 3 are more favourable.

1400

1200

1000

800

600

400

200

0 ix al er m idu ow ity es p tric r nd c dic i ele or W ic N rd No

FigureFigure 6. 6. Emissions for for one one year year for for Case Case 1 (blue), 1 (blue), Case Case 2 (red), 2 (red), and Case and Case3 (yellow) 3 (yellow) for different for diffperspectives.erent perspectives.

The low energy use is a result of the ectogrid technology, which enables a reduction in energy The low energy use is a result of the ectogrid™™ technology, which enables a reduction in energy use in areas with both heating and cooling demands. Case 3 has the lowest impact because geothermal use in areas with both heating and cooling demands. Case 3 has the lowest impact because solutions have the potential to store energy in the ground in order to decrease the energy supply to geothermal solutions have the potential to store energy in the ground in order to decrease the energy the system. supply to the system. AA combination combination of of a geothermala geothermal energy energy solution solution and and ectogrid ectogrid™™ would would probably probably be be the the most most energy-eenergy-efficientfficient solution solution with with the lowest the lowest climate climate impact. impact. Looking Looking into the future,into the when future, more when electricity more willelectricity probably will be probably produced be by produc renewableed by energyrenewable sources, energy solutions sources, with solutions low electricity with low electricity use will be use favourablewill be favourable from an environmental from an environmental point of view. point of view. 5.2.3. A European Context 5.2.3. A European Context In a European context, it is likely that the heating demand is met by local gas boilers, and the In a European context, it is likely that the heating demand is met by local gas boilers, and the cooling demand is met by air-conditioners [39]. The emission factors in this example represent the cooling demand is met by air-conditioners [39]. The emission factors in this example represent the European electricity mix [40] and the combustion of natural gas [41]. These are presented in Table5. European electricity mix [40] and the combustion of natural gas [41]. These are presented in Table 5. The demand profile for Medicon Village has been used in the comparison. The demand profile for Medicon Village has been used in the comparison. Table 5. Emission factors for the European residual electricity mix and natural gas. Table 5. Emission factors for the European residual electricity mix and natural gas. Emission Factor Scenario Emission Factor Scenario (g CO2 equivalent/kWh) (g CO2 equivalent/kWh) European electricity mix [40] 522.0 Combustion ofEuropean natural gas electricity in a local boiler mix [40] [41] 227.0522.0 Combustion of natural gas in a local boiler [41] 227.0 The results of the calculations can be seen in Figure 7. The case denoted as gas and air- The results of the calculations can be seen in Figure7. The case denoted as gas and air-conditioners conditioners indicates that the heating demand is met by gas in local boilers and the cooling demand indicates that the heating demand is met by gas in local boilers and the cooling demand is met by is met by air-conditioners with a COP value of 3. The total emissions are considerably larger for all air-conditioners with a COP value of 3. The total emissions are considerably larger for all the cases the cases compared to the results shown in Sections 5.1, 5.2.1, and 5.2.2. If the solution with gas boiler compared to the results shown in Sections 5.1, 5.2.1 and 5.2.2. If the solution with gas boiler and and air-conditioners can be assumed to represent the current situation in many places in Europe, air-conditioners can be assumed to represent the current situation in many places in Europe, there are there are possibilities to reduce the emissions through implementing ectogrid™ or geothermal possibilities to reduce the emissions through implementing ectogrid™ or geothermal systems. systems. Sustainability 2019, 11, x FOR PEER REVIEW 14 of 17 Sustainability 2019, 11, 7051 14 of 17

3000

2500

2000

1500

1000

500

0 2 3 er se se ion Ca Ca dit on r-c ai nd s a Ga

FigureFigure 7. 7.Emissions Emissions for for one one year year for for the the di ffdiffererentent cases cases in in a Europeana European context. context. The results of the case study with the Swedish conditions show that emissions can be reduced The results of the case study with the Swedish conditions show that emissions can be reduced by 70 tons of CO2 equivalents by implementing ectogrid™ and by 115 tons of CO2 by implementing by 70 tons of CO2 equivalents by implementing ectogrid™ and by 115 tons of CO2 by implementing a geothermal solution, compared with the emissions from district heating and district cooling (see a geothermal solution, compared with the emissions from district heating and district cooling (see Figure4). At the same time, this analysis demonstrates that a shift to ectogrid ™ and geothermal Figure 4). At the same time, this analysis demonstrates that a shift to ectogrid™ and geothermal energy in a European context can give even larger reductions. By changing from the gas boiler and energy in a European context can give even larger reductions. By changing from the gas boiler and air-conditioner solution to ectogrid™, 990 tons of CO2 equivalents can be saved. By changing to air-conditioner solution to ectogrid™, 990 tons of CO2 equivalents can be saved. By changing to a a geothermal solution, 1250 tons of CO2 equivalents can be saved. This corresponds to reductions of geothermal solution, 1250 tons of CO2 equivalents can be saved. This corresponds to reductions of 24% and 33%, respectively. In central Europe, where there is often a larger cooling demand than in 24% and 33%, respectively. In central Europe, where there is often a larger cooling demand than in Sweden, there are potentially better balancing opportunities that can be exploited by ectogrid™ to Sweden, there are potentially better balancing opportunities that can be exploited by ectogrid™ to reduce the demand for supplied energy. reduce the demand for supplied energy. 6. Discussion 6. Discussion 6.1. Some Aspects of the Data 6.1. Some Aspects of the Data The calculations of the energy use are based on measurements of the heating and cooling used by eachThe building calculations in Medicon of the Village.energy use In order are based to obtain on measurements more information of the regarding heating and the energycooling useused ofby the each diff erentbuilding energy in Medicon systems, Village. data for In Case order 1, Caseto obtain 2, and more Case information 3 have been regarding prepared the in energy different use ways.of the For different Case 1, energy the energy systems, company data for Kraftringen Case 1, Case [28] 2, has and shared Case data3 have on been the district prepared heating in different and coolingways. network.For Case 1, Data the wereenergy given company in the Kraftringen form of ratios [28] (percentages) has shared data between on the the district energy heating used byand thecooling pump network. and the energyData were delivered given in to the the form pump. of ratios Similar (percentages) percentages between for energy the energy losses areused given by the bypump [2], which and the indicate energythat delivered the values to the obtained pump. Simila from [r28 percentages] can be seen for as energy representative losses are data.given Databy [2], havewhich also indicate been given that the in thevalues form obtained of actual from data [28] on ca producedn be seen districtas representative heating and data. district Data cooling.have also Forbeen Case given 2, the in datathe form are based of actual on howdata E.ONon produced [30] intends district for heating the system and todistrict function, cooling. based For on Case the 2, conditionsthe data are of the based diff erenton how system E.ON components [30] intends and for thethe lawssystem of thermodynamicsto function, based [29 on]. the For conditions Case 3, the of systemthe different is approximated, system components based on reasonable and the assumptionslaws of thermodynamics with the support [29]. of For expertise Case 3, in the geothermal system is solutionsapproximated, [26]. based on reasonable assumptions with the support of expertise in geothermal solutionsAnother [26]. important parameter is COP. COP values have been derived from datasheets from manufacturersAnother ofimportant heat pumps parameter and cooling is COP. machines. COP valu Thesees have theoretically-calculated been derived from datasheets COP values from probablymanufacturers do not exactly of heat match pumps the actualand cooling values, butmachin theyes. can These be assumed theoretically-calculated to be reasonable assumptions COP values forprobably the calculations. do not exactly match the actual values, but they can be assumed to be reasonable assumptions for the calculations. 6.2. Analysis of Environmental Impact 6.2. Analysis of Environmental Impact The environmental evaluation shows that the geothermal energy solution has the lowest climate impact.The This environmental is because of evaluation the advantage shows of storingthat the energy geothermal in the energy ground. solution ectogrid has™ thehas lowest the second climate impact. This is because of the advantage of storing energy in the ground. ectogrid™ has the second Sustainability 2019, 11, 7051 15 of 17 lowest climate impact because of the increased capacity of the heat pump when both a heating and a cooling demand can be fulfilled simultaneously. Even if the conventional district heating and cooling uses a lot more energy than ectogrid™ and the geothermal solution, the climate impact does not differ that much between the cases. The reason is that it is favourable from an environmental perspective to use heat for heating instead of electricity. Another possibility would be to combine ectogrid™ with a geothermal solution by replacing the active balancing unit. This makes it possible to balance the energy demand between different seasons and decrease the energy supply to the system. In further work, it would be interesting to evaluate this combination from an environmental perspective. The use of renewable energy resources for electricity and district heating production increases continuously. This will lead to a lower climate impact for all three cases. Combinations of existing energy solutions with new, more efficient energy solutions (e.g., ectogridTM) could lead to even more environmentally friendly energy solutions for buildings. The analysis from a European perspective shows that the potential for reducing the climate impact, by using more energy efficient solutions in buildings, is high in Europe.

6.3. Wider Perspective The results from this study cannot necessarily be transferred to other areas with other conditions. District heating is a favourable solution from an exergy point of view in areas that are characterized mainly by a heat demand. ectogrid™ is a more efficient solution when the buildings have diverse heating and cooling demands with balancing potential. A geothermal solution is energy efficient, but disadvantages include the requirement for specific ground conditions and also high implementation costs. Different conditions in different areas make it profitable to develop different types of of energy solutions. There are several systems that are adapted to the conditions and demands of the future. In this study, ectogrid™, cold district heating, and efficient heat pump solutions are some examples. The fact that electricity production heads towards using more renewable energy sources, with lower emissions, makes it more acceptable to use electricity for heating. More renewable electricity production means more intermittent energy, which leads to a need for energy solutions that can use the electricity when it is available. With this energy evolution, it will be advantageous to use heat pumps for heating and cooling, because heat pumps can use electricity efficiently to eliminate diverse energy demands. Another advantage is that they can use available intermittent energy by utilizing the thermal inertia of the buildings. The ongoing energy evolution changes the focus of how to evaluate an energy solution. That is, from having an exergy perspective to instead having an energy resource perspective.

7. Conclusions The results of this study indicate that the geothermal solution should be the best for Medicon Village from an environmental point of view (see Table6). However, as the geothermal solution is fictitious, it is also the case with the most uncertainties in the calculations. The ability of the geothermal solution to store energy in the ground between seasons has advantages from an energy perspective. Even though a smart energy solution, according to ectogridTM, does not use seasonal storage, energy use does not differ substantially compared to the geothermal solution. A possible improvement of the solution for Medicon Village could be to combine ectogrid™ with a geothermal solution in order to take advantage of both the balancing of energy between buildings and the seasonal storage. This could result in a system with very low energy use. Sustainability 2019, 11, 7051 16 of 17

Table 6. Summary of results.

Energy Use Emission Case (MWh) (tons of CO2 equivalents) Conventional district heating and cooling 12,253 590 Smart energy solution for heating and 4713 510 cooling (ectogrid™) Geothermal energy 3612 470

The study can hopefully give an increased understanding of how energy solutions can interact with each other. More options for heating and cooling will increase the possibility to choose the energy solution that is best suited to different needs and conditions of different areas. In this way, we can fulfil our heating and cooling demand while at the same time minimize the environmental impact.

Author Contributions: Conceptualization, I.F. and L.N.; methodology, I.F. and L.N.; software, I.F.; validation, I.F. and L.N.; formal analysis, L.N.; investigation, L.N.; data curation, I.F.; writing—original draft preparation, I.F. and L.N.; writing—review and editing, M.A.; visualization, I.F. and L.N.; supervision, M.A. Funding: This research received no external funding. Acknowledgments: The authors gratefully acknowledge E.ON innovation in Malmö for the possibility of conducting this study and for valuable and constructive suggestions during the work, and Danica Djuric Ilic at Linköping University for her support in the energy system analysis. Conflicts of Interest: The authors declare no conflict of interest.

References

1. IPCC. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; IPCC: Geneva, Switzerland, 2014. 2. Frederiksen, S.; Werner, S. District Heating and Cooling, 1st ed.; Studentlitteratur: Lund, Sweden, 2013. 3. Värmemarknadskommittén. Överenskommelse i Värmemarknadskommittén 2018; Energiföretagen Sverige: Stockholm, Sweden, 2018. 4. Gode, J.; Byman, K.; Persson, A.; Trygg, L. Miljövärdering av el ur Systemperspektiv; IVL Svenska Miljöinstitutet: Stockholm, Sweden, 2009. 5. E.ON. ECTOGRIDTM. Available online: http://ectogrid.com/ (accessed on 21 November 2019). 6. E.ON. The ECTOGRIDTM technology. Available online: http://ectogrid.com/business-customer/ (accessed on 21 November 2019). 7. Game Changing Technology Connects Medicon Village Buildings. Available online: https:// www.mediconvillage.se/sv/game-changing-technology-connects-medicon-village-buildings (accessed on 21 November 2019). 8. Kadir, S.; Özkan, S. ECTOGRIDTM. The Competitiveness of a Low Temperature District Network in Germany and United Kingdom. Master’s Thesis, KTH Industrial Engineering and Management, Stockholm, Sweden, 21 February 2018. 9. Alvarez, H. Energiteknik Del II, 3rd ed.; Studentlitteratur: Lund, Sweden, 2006. 10. Werner, S. Energiförsörjning, 1st ed.; Studentlitteratur: Lund, Sweden, 2016. 11. IEA Heat Pump Center. Heat Pump Concepts for Nearly Zero-Energy; IEA Heat Pump Center: Borås, Sweden, 2016. 12. Fernández, F.J.; Folgueras, M.B.; Suárez, I. Energy study in water loop heat pump systems for office buildings in the Iberian Peninsula. Energy Procedia 2017, 136, 91–96. [CrossRef] 13. Omer, A.M. Ground-source heat pumps systems and applications. Renew. Sustain. Energy Rev. 2008, 12, 344–371. [CrossRef] 14. Spitler, J.; Bernier, M. Vertical borehole ground design methods. Adv. Ground-Source Heat Pump Syst. 2016, 29–61. [CrossRef] 15. Gehlin, S. Borehole thermal energy storage. Adv. Ground-Source Heat Pump Syst. 2016, 295–327. 16. Kim, Y.; Lee, J.; Jeon, S. Hybrid ground-source heat pump systems. Adv. Ground-Source Heat Pump Syst. 2016, 331–357. [CrossRef] Sustainability 2019, 11, 7051 17 of 17

17. Akhlaghi, S.; Carlson, S. Mot Fjärde Generationens Fjärrvärme: En Fallstudie av Möjliga Lösningar i Malmö; Lunds universitet: Lund, Sweden, 2016. 18. Lund, H.; Werner, S.; Wiltshire, R.; Svendsen, S.; Thorsen, J.E.; Hvelplund, F.; Mathiesen, B.V. 4th Generation District Heating (4GDH): Integrating smart thermal grids into future systems. Energy 2014, 68, 1–11. [CrossRef] 19. Bünning, F.; Wetter, M.; Fuchs, M.; Müller, D. Bidirectional low temperature district energy systems with agent-based control. App. Energy 2018, 209, 502–515. [CrossRef] 20. Karlsson, B.; Lundström, L.; Eriksson, O. Energivärdering av Byggnader; Fjärrsyn Svensk Fjärrvärme: Stockholm, Sweden, 2016. 21. Pellegrini, M.; Bianchini, A. The Innovative Concept of Cold District Heating Networks. 2018, 11, 236. [CrossRef] 22. EME Analys AB and Profu in Göteborg AB. Miljövärdering av el—Med Fokus på Utsläpp av Koldioxid; Elforsk AB: Stockholm, Sweden, 2017. 23. Energi, S. Vägledning Angående Ursprungsmärkning av el; Energiföretagen: Stockholm, Sweden, 2012. 24. Gode, J.; Martinsson, F.; Hagberg, L.; Öman, A.; Höglund, J.; Palm, D. Miljöfaktaboken 2011—Uppskattade Emissionsfaktorer för Bränslen, el, Värme och Transporter; Värmeforsk Service AB: Stockholm, Sweden, 2011. 25. E.ON Is Building the World’s First ECTOGRIDTM at Medicon Village. Available online: http://ectogrid.com/ use-cases/medicon-village/ (accessed on 22 November 2019). 26. Ekestubbe, J.; (E.ON, Malmö, Sweden). Personal Communication, 12 March 2018. 27. Microsoft Excel for Office; Microsoft Corporation: Redmond, WA, USA, 2018. 28. Gierlow, M.; (Kraftringen Energi, Lund, Sweden). Personal Communication, 7 March 2018. 29. Alvarez, H. Energiteknik Del I, 2nd ed.; Studentlitteratur: Lund, Sweden, 2003. 30. Rosén, P.; (E.ON, Malmö, Sweden). Personal Communication, 1 March 2018. 31. Storck, K.; Karlsson, M.; Andersson, I.; Renner, J.; Loyd, D. Formelsamling i termo-och Fluiddynamik; Linköping University: Linköping, Sweden, 2010. 32. Holm & Holm. Wall Thickness and Weight of PE Pipes. Available online: https://www.holm-holm.dk/en/ plastic-info/wall-thickness/ (accessed on 14 February 2018). 33. The Engineering Toolbox, 2003. Thermal Conductivity of Common Materials and Gases. Available online: https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html (accessed on 14 February 2018). 34. Commercial Refrigeration. Available online: https://www.carrier.com/commercial-refrigeration/en/uk/ solutions/ (accessed on 15 June 2018). 35. Martinsson, F.; Gode, J.; Arnell, J.; Höglund, J. Emissonsfaktor för Nordisk Elproduktionsmix. IVL; Svenska Miljöinstitutet: Stockholm, Sweden, 2012. 36. Kraftringen, Fjärrkyla. Available online: https://www.kraftringen.se/hallbarhet/miljo-och-klimat/produkter- och-tjanster/Fjarrkyla/ (accessed on 26 February 2017). 37. Energiföretagen. Miljövärdering av Fjärrvärme. Available online: https://www.energiforetagen.se/statistik/ fjarrvarmestatistik/miljovardering-av-fjarrvarme/ (accessed on 15 June 2018). 38. Residualmixen Tidigare år. Available online: https://www.ei.se/sv/for-energiforetag/el/ursprungsmarkning- av-el/residualmixen-tidigare-ar/ (accessed on 15 April 2018). 39. EcoHeatCool. The European Heat Market; Ecoheatcool and Euroheat & Power: Brussels, Belgium, 2006. 40. RE-DISS: European Residual Mixes 2015; Association of Issuing Bodies: Brussels, Belgium, 2016. 41. Busato, F.; Lazzarin, R.M.; Noro, M. Energy and economic analysis of different heat pump systems for space heating. Int. J. Low-Carbon Technol. 2012, 7, 104–112. [CrossRef]

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).