Solar Heat for Large Buildings Guidelines and Practical Examples for Apartment Buildings, Hotels and Business This publication was compiled as part of the EU SOLARGE project Foreword Rising oil and gas prices,climate change and growing energy import dependency place our current energy supply arrangements under increasing threat. A major challenge for the future is to cut fossil fuel use to a minimum. About a third of Europe’s final energy con- sumption is accounted for by space and water heating in buildings. Conserving energy and using renewables in this sector can reap mas- sive cost savings and are an efficient way to help slow climate change. This brochure is intended for building planners in the residential building,hotel and local government sector who aim to make buildings ready for the solar age. It presents examples of large solar thermal systems across Europe together with experience gathered in operat- ing them. The brochure has been produced as part of the European SOLARGE project, in which eleven organisations from eight countries around Europe use a wide range of measures to pro- mote solar thermal systems in apartment buil- dings,hotels and municipal facilities.The examples are intended to encourage similar projects and invite replication. The SOLARGE Team www.solarge.org Contents Foreword Y 3 Best Practice Catalogue Y 24 Large Solar Thermal Systems Y 6 Hot Water Systems Y 26 Fields of Application Y 8 Hot Water and Space Heating Sytems Y 50 Components Y 10 Other Applications Y 64 System Approaches Y 14 Heating Circuits Y 16 Outlook Y 68 Costs of Solar Thermal Y 18 Publisher's Information Y 70 Systems Planning Procedure Y 20 Solar Air Conditioning in Y 22 a Nutshell Technical Basics Large Solar Thermal Systems The great majority of solar thermal systems Solar thermal: market development now in use belongs to detached or semi- The use of solar thermal heating has spread detached houses. rapidly in recent years.Solar systems with a But solar thermal systems are increasingly total collector area of some 19 million square being used in larger buildings: apartment metres are now installed across Europe.This blocks,hotels and catering establishments, impressive figure shows the technology has and public buildings. long matured and is established in the market. Many large systems are already installed in The European Solar Thermal Industry Federation Europe.The experience gained with these (ESTIF) forecasts that total installed collector systems is so positive that many operators area will increase by 30 % a year over the long are planning more systems. term. However, market penetration varies One important lesson learnt is that the design greatly between different EU states. of large solar systems cannot be standardised. Each system must be individually designed, taking into account the circumstances and user needs. A task and a challenge for all architects and engineers involved. Electricity 15 GWth GWth/a Growth of solar 20 % 6 thermal energy Heat 10 1.5 in Europe 49 % Solar thermal Transport energy is booming. 5 31 % Over 19 million square metres About half of final 0 0 (13.5 GWth) of solar energy consump- 9798 99 00 0102 03 04 0506 collectors were in operation across tion is used in in operation Europe by 2006. generating heat, newly installed most of it for buil- Source: ESTIF dings. p Flat plate collectors Photo: Conergy Technical Basics Fields of Application Solar thermal energy can be used wherever Public buildings low-grade heat is needed: For hot water, to Sports facilities,old people’s homes and swim- supplement space heating, and to generate ming pools are generally well suited to solar process heat for thermally driven air conditio- thermal energy because they need hot water ning systems. in large quantities. As administrative buildings Solar thermal systems can supplement the mostly only need space heating, solar thermal supply of heat to buildings in summer,late systems are not suitable for such buildings spring and early autumn. unless air conditioning is required. Apartment buildings Hotels and restaurants Large solar thermal systems on apartment Hotels are very well suited to the use of solar buildings in Europe are mostly used to provide thermal energy because they tend to be hot water. In central and northern regions of busiest in the summer months and in late Europe there is also a trend towards ‘combi- spring and early autumn. systems’ that supplement space heating. Solar energy is also useful to hotels and restaurants as a marketing instrument to attract environment-conscious tourists. 8 Apartment building,Salzburg,Austria Hotel du Golf de Valescure, France Photo: S.O.L.I.D./Austria Solar Car wash Center in Oberursel,Germany Photo:Wagner-Solar.com Swimming pools Car washes Solar water heating in hotels combines ex- Solar thermal systems provide a simple way of cellently with water heating for swimming heating water for car washes. Heating the pools. Surplus heat is easily transferred to water also saves on detergent .It may make pool water, improving user comfort at no extra sense to connect repair shops and showrooms energy cost. into the solar system to smooth heat demand over time. Solar air conditioning Hotels and restaurants often have large air Solar thermal energy for contractors conditioning needs,as do as hospitals and Solar thermal energy is also attractive as a public buildings. Solar thermal energy can product for energy suppliers and contractors. be used here in existing thermally driven air They can install collectors on factory,ware- conditioning systems. house and residential roofs or on spare land and sell the generated heat to consumers or a district heating network.This makes for predictable energy prices and stable heat generation costs for district heat, in both cases for the long term. 50 m Overnight stays in 2003 40 30 20 10 0 12 3 4 5 6 7 8 9101112 Bed occupancy Solar power Bed occupancy and solar power UPC Arena Graz,Austria: In many hotels (chart: Germany) Local heat management contracted to nahwaerme.at hot water consumption tracks solar energy availability over the year. Photo: S.O.L.I.D./ ESTIF Source: Federal Statistical Office 2005 Technical Basics Components Collectors and Storage tanks Collectors A roof-mounted solar collector captures sunlight and converts it into heat.The unit’s absorber has what is called a selective surface coating, allowing it to convert even diffuse or winter day solar radiation into heat energy with high efficiency.The collector is protected by tempered glass which can withstand even hailstones. Collectors can be mounted on a flat or pitched roof,integrated into the roof cladding or installed as part of the building’s facade. Most modern solar thermal systems use flat plate or vacuum tube collectors.The required system temperatures as well as the moun- ting mode determine the type of collector. Collector types overview Collector Type Heat Transfer Medium Applications 10 Air collector Air Preheating for factory shed air-drying systems,‘open’ air conditioning systems,and solar drying Glazed flat-plate collector Water or Hot tap water,space heating,so-called ‘open’ and ‘closed’ single-stage water-glycol mixture air conditioning/chiller systems and preheating of industrial processes Vacuum tube collector Water or Hot tap water,space heating,single-stage and two-stage air conditioning/ (direct flow) water-glycol mixture chiller systems and preheating of industrial processes Vacuum tube collector Indirect heating of the Hot tap water,space heating,single-stage and two-stage air conditioning/ (heat pipe) heat transfer medium chiller systems and preheating of industrial processes (Water or water-glycol mixture) Heat storage Seasonal storage Short-term storage Seasonal thermal storage is mostly used in Short-term storage units store captured solar district heating networks and can retain heat heat for several days to make up for rainy for several weeks.There are hot water, gravel/ weather.Good temperature stratification is an water,borehole and aquifer systems. important factor in such units.They are there- Hot water tanks used in seasonal heat storage fore made tall and slender so stable strata are several thousand cubic metres in volume. spanning a large temperature range can be Seasonal storage is mostly used in residential built up over their height . Collector return flow areas with hundreds of individual apartment temperatures should be as low as possible. buildings,but latterly as well as in separate This is a precondition for high system efficien- apartment buildings. Seasonal storage allows cy.Solar thermal energy can be made to cover solar energy to meet up to 100 % of total heat up to 30 % of total heat demand. demand. Solar thermal storage tanks 100 % solar-heated apartment building (under construct- ion), by Jenni Energietechnik – completed in August 2007 Photo: Jenni Energietechnik AG,Switzerland Seasonal thermal storage technologies Borehole heat storage Gravel/ water heat storage Aquifer heat storage Solar heat is transferred to Pits lined with special This form of storage uses the ground via boreholes sheeting are filled with a groundwater to store thermal 20–100 metres deep and is gravel/ water mixture.The energy.Groundwater raised drawn upon as needed. Due heat is transported to the from a borehole is warmed by to the lower thermal capacity store by the water itself a heat exchanger and then of soil, the stores are general- or through coiled pipes. returned to the aquifer via a ly three to five times larger Gravel/ water storage has second borehole.The heat is than hot water units. How- a lower heat capacity than recovered by reversing the ever they are less complicated straight hot water storage flow.The cost per unit heat to build and can be extended units and needs a bigger generated is relatively low, as needed.