GLA Renewable and Decentralised Energy Potential Study
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London’s Zero Carbon Energy Resource: Secondary Heat Report Phase 2 April 2013 Secondary Heat study Phase 2: Network and System impacts Copyright Greater London Authority April 2013 Greater London Authority City Hall The Queen’s Walk More London London SE1 2AA www.london.gov.uk enquiries 020 7983 4100 minicom 020 7983 4458 This report has been led by Buro Happold Ltd, working in collaboration with the Greater London Authority and supported by DEC Engineering, Canada, and COWI, Denmark. Team Advisory Panel The Greater London Authority London First David Leam Peter North UK Power Networks Liam O’Sullivan Ross Hudson Environment Agency Marius Greaves Buro Happold Ltd Mick Flynn Alasdair Young Transport for London Mark Gilbey Henrietta Cooke Crossrail Mike de Silva Chris Grainger Thames Water Graeme Walker DEC Engineering Ltd, Canada Land Securities Neil Pennell Erik Lindquist Institute for Sustainability Martin Gibbons COWI, Denmark Poul Weiss Industry Representatives J&E Hall International John Shennan Star Refrigeration David Pearson Greater London Authority Secondary Heat study Phase 2: Network and System impacts Revision Description Issued by Date Checked 00 Draft for comment AY 08/03/13 GS 01 Final HC 04/04/13 AY 02 Final review CG 18/07/13 AY report collation Chris Grainger signature date 18/07/13 report checking Henrietta Cooke signature date 18/07/13 report approval Alasdair Young signature date 18/07/13 GLA approval Ross Hudson signature date Greater London Authority Secondary Heat study Phase 2: Network and System impacts Executive summary The Greater London Authority (GLA) has commissioned a study into the capacity and utilisation of secondary heat sources in London. For the purposes of this study, secondary heat is considered to be heat arising as a by-product of industrial and commercial activities, from infrastructure operation, and from the environment (air, ground, water). This study builds on the Mayor’s Decentralised Energy Capacity Study (2011) 1 which suggests that by 2030 22% of London’s heat and electrical energy could be generated by decentralised energy sources linked to heat networks. Sources of this heat are likely to be combustion of primary fuels including gas, biomass and waste. With the likely reduction in availability and viability of gas, and possibly waste, there will be an increasing emphasis on alternative sources, of which secondary heat is one. Further to this as gas fired combined heat and power ceases to be a low carbon option from around 2030 zero carbon heat sources are required to ensure heat networks do not become stranded assets. In the first phase of this study the London wide potential for secondary heat sources was addressed. The objectives of this report are to provide an understanding of the impacts on buildings and heat networks of utilising these secondary sources of heat via low temperature heat networks. This report also addresses the cost and environmental benefits of each heat source and explores emerging spatial and project opportunities for using secondary heat. 1 GLA (2011) Decentralised Energy Capacity Study: http://www.london.gov.uk/priorities/environment/climate-change/decentralised- energy Greater London Authority i Secondary Heat study Phase 2: Network and System impacts Key Findings 1 Most secondary heat sources need upgrading to higher temperatures to be useable in heat networks, this requires heat pumps. 2 The minimum suitable operating temperature for heat networks is 55°C 3 From the Phase 1 study, secondary heat sources in London can provide up to 71TWh/yr of heat at 70°C, of which 50 TWh/yr is attributed directly to the heat sources and 21TWh/yr to the electricity required by heat pumps. This quantity of heat exceeds London’s 2010 heat demand of 66TWh/yr. 4 When compared to more conventional centralised gas boiler heating, 12 TWh/yr of secondary heat across London can be considered ‘cost effective’. This is equivalent to 18% of London’s 2010 heat demand. 5 When compared to more conventional centralised gas boiler heating, 56 TWh/yr of secondary heat can be considered ‘CO 2 effective’. This is equivalent to 56% of London’s 2010 heat demand. 6 A pilot study are in Barking and the Royal Docks suggests that secondary heat sources which are of a lower cost and carbon intensity than gas boilers (under a 2010 scenario) can demonstrate a 73% saving in the energy required for heating in this area, and a 48% saving in associated CO 2 emissions. Greater London Authority ii Secondary Heat study Phase 2: Network and System impacts Summary Carbon Intensity For most secondary heat sources it is necessary to upgrade the temperature of available heat to be usable directly within district heating systems – this requires the use of heat pumps. The carbon intensity of secondary heat is therefore directly related to the carbon intensity of the electricity supply driving the heat pumps in these cases. Section 2 explores the cost and carbon intensity of heat from secondary sources. The efficiency of heat pumps (modelled as co-efficient of performance) is heavily dependent on the input (‘available’) and output (‘delivered’) temperatures. Heat pump efficiency increases by around 80% when input temperatures increase from 5CC to 35CC. The operating temperature of heat networks is also very important. For example heat pumps supplying heat at 55CC are around 25% more efficient than heat pumps supplying heat at 70CC. Future projections of carbon factors consider the decarbonisation of the electricity grid network and as such, heat pumps connected to secondary sources can deliver heat at 70°C and still offer significant carbon savings. For 2030 and 2050 scenarios the heat carbon intensity of heat pumps is below 0.05tCO 2/MWh, four times less than the equivalent heat from large gas boilers and in for most sources it is much lower than this. The carbon intensity is lower than individual air source heat pumps in all cases. Cost Approximately one third of the secondary heat sources explored in this study have a lower levelised cost than that of the counterfactual gas boiler case at current prices. Viable sources include heat recovery from supermarkets, power stations, national grid substations and data centres. 12 TWh/yr of secondary heat can be considered ‘cost effective’ under a 2010 BAU scenario; this is equivalent to 18% of London’s 2010 heat demand. Sources more expensive than the counterfactual case are dominated by the environmental sources such as air and river. As with carbon, the cost of heat from secondary heat sources is linked to the need to upgrade their temperature for effective use. Future costs associated with the use of these sources are highly dependent on electricity prices, but less so than individual heat pumps due to their higher efficiency. The opportunity to use heat pumps connected to heat networks also increases their utilisation (or run hours or load factor) which significantly reduces the cost of heat. In the short term secondary heat system projects should focus on recovering heat at the highest possible temperatures, including heat from industry and existing gas engine generators. These sources also provide the lowest cost of heat and can often be used directly. All cost calculations assume that no financial incentives are available and that networks are pre- existing at the time of construction (and so not costed) as it was considered unlikely that secondary sources could support the investment costs of heat networks. This strategy has been taken to reduce the number of estimated variables, to provide baseline recommendations only. Effects of financial incentives and network costs have been discussed qualitatively. Electricity and gas price projections are based on DECC scenarios; these are discussed in more detail in the Phase 1 report. Greater London Authority iii Secondary Heat study Phase 2: Network and System impacts Building connections and performance Decreasing heat network temperatures increases heat pump efficiency. The minimum suggested network operating temperature is 55°C. To maximise the amount of London’s current building stock that can connect to secondary heat networks, a compromise of 70°C has been used for modelling purposes. A number of generic building types were modelled (see Section 3) to explore the implications of connecting to lower temperature networks. For the buildings modelled, a flow temperature of 55°C was judged the lowest practical temperature for connecting to heat networks without replacing their internal heating systems. Below this temperature the fraction of heating load which can be met reduces significantly, as well as introducing concerns regarding legionella disinfection. A flow temperature of 55 °C could be used to supply at least 70% of the annual existing building heat consumption in residential buildings and more in non-residential buildings. This represents around half the peak heat load, for which either supplementary heat sources would be required, or network temperatures boosted, to supply around 85 °C for short periods. In most cases improvements in energy efficiency, equivalent to an increase in one Energy Performance Certificate (EPC) band, could enable almost 100% of heating demand to be met from flow temperatures of 55°C or above. Practical applications decrease significantly below 55°C - heat supply temperatures of 40°C can only supply a minority of annual heat demand, even with extensive retrofit; they cannot supply domestic hot water. Only electrical transformer and industrial sources are considered available at or above 55 CC meaning heat pumps are required for all other sources. System design Using secondary heat sources requires the use of low temperature heat networks to maximise carbon savings and minimise the cost of heat. The focus of system design should be on ensuring low return temperatures to the district network. This is key to enabling the use of low temperature secondary heat and building heating systems must be designed to comply with best practice guidelines to ensure this.