FAQs: Bunhill energy centre and heat network Q. Why have we set up an energy centre and heat network in Bunhill? A. We set up a heat network in the Bunhill ward to provide cheaper, greener, locallyproduced heat to warm more than 850 nearby homes, a swimming pool and a leisure centre. The heat network is fed by a local energy centre, which produces electricity and heat. In the same way that we use heat from a car engine to keep us warm when driving, the energy centre uses the heat created from producing electricity to help heat buildings and provide hot water. The central power stations that produce most of our electricity waste up to two thirds of their energy, mostly through wasted heat. The existing energy centre produces electricity on a much smaller scale and the otherwise wasted heat is captured and piped around the heat network. This makes the energy centre much more efficient, cheaper and greener - providing residents with cheaper warmth and helping us reduce our carbon emissions. If you would like to find out more about the Bunhill Heat Network please watch our video. Q. What exactly is a local heat network? A. A local heat network is a series of underground pipes carrying hot water between the local energy centre (where the heat is generated) and the buildings connected to the network. The heat network consists of two parallel pipes, one carrying hot water to buildings in the network and the other returning the cooler water back to the energy centre. The heat is transported through these pipes to the boiler houses in each building. In the boiler house, the heat is transferred into the existing central heating and hot water systems using plate heat exchangers which in turn supply the heat and hot water to each building. Q. What is Bunhill extension? A. Following the success of the Bunhill Energy Centre (Bunhill I) Islington has investigated potential extensions. These feasibility studies identified local urban waste heat produced from London Underground and an electricity substation to supply additional heat to an extension of the heat network. These systems may now be supported by a second CHP plant installation. The extension will provide cheaper heat to a further 454 homes at the King s Square estate, and would like to supply more than a thousand more homes. The extension (Bunhill II) is planned to also serve a school, sheltered housing block, a community centre and a nursery. Discussions are also underway with other buildings that could benefit. The energy centre and heat network will start in summer 2015.
Q. Where will it happen? A. We plan to extend the existing heating pipe network from Bunhill Energy Centre up Central Street to City Road to capture waste heat from the tube network and an electricity substation. A new energy centre will be built on the junction of Moreland Street and Central Street next to Kestrel House on the East side, where a small building currently stands. We will be talking to local residents about these proposals shortly.we are aware that there will be some disruption during installation but we will be working to reduce any inconvenience to you. We will keep as much construction as possible off site, for example by putting parts of the energy centre together before they arrive. We will write to you to keep you informed of what is happening and when. We are also working with architects and an artist to make the energy centre look as attractive as possible. More information will be available shortly. Q. What are the benefits for those connected to the heat network? A. We are looking into connecting estate blocks in Kings Square to the heat network. There are several benefits for homes connecting to the network: Reduced energy costs We expect that your heating bills will be cheaper than if you were not connected to the network, with previous schemes reducing costs by about 10%. The existing energy centre uses the heat that most power stations waste when generating electricity (up to two thirds of the energy can be wasted in traditional power stations). The electricity generated is sold to the national grid, offsetting the price paid for gas fuel to run the energy centre. This is more efficient so savings can be passed on to residents. Greater energy reliability and security The existing boilers in the council buildings are retained to provide an additional source of heat (e.g. on a very cold day) and as back-up. Having two heat sources increases the security and reliability of the heat network (e.g. for when a heat source is being maintained) and builds in flexibility of how we can run the network at different times of the day to ensure the cheapest possible operation of the network. This can in turn be passed onto our residents through cheaper energy bills. In addition to this buildings connected to the network have two independent sources of heat, the network or their retained gas boilers. This means that if a fault develops in one (e.g the gas boilers) heat may be supplied from the network to prevent an interruption of the space heating or hot water service.
Reduced carbon footprint The existing CHP is the most efficient way to get the most out of the fuel that we use (currently gas) and so can result in 30 per cent less carbon dioxide emissions than traditional heat and power supplies. The addition of waste heat from heat pumps also offers a low carbon source of heat to the network. The heat pumps only use 1 unit of electricity to make 3-4 units of heat, and is therefore 300-400% more efficient than direct electric heating, as well as lower carbon than conventional gas boilers. Furthermore low cost electricity (off peak, e.g. overnight) is associated with a greater proportion of renewable electricity generation, therefore is also a lower carbon energy supply for the heat pumps. Q. How will joining to the local heat network affect connecting residents? A. You will not be recharged for the cost of building the heat network or connecting it to your estate. The new network will be connected to your estate's existing boiler house so we are not anticipating having to do any work inside peoples home and there will be no new pipes to homes as a result of these works. There will be no change to the heat and power people receive at home, and little or no disruption to heat and power supplies. Q. Will heat to homes be turned off? A. There should be no disruption to heat or hot water supplies to homes during the construction of the heat network. There may be a few hours that the boilers need to be turned off to connect to the network but this period will be planned to be minimised and where possible will not be done during the heating season. Residents will be given prior notice if this is required. Q. Will the heat at homes be different? A. The heat that people receive in their homes will remain the same, the only difference is where the heat has come from. Instead of using the gas boilers in the boiler room on the estate the heat network will provide heat to the boiler room in exactly the same way that the gas boiler would. Q. Can I opt out? A. The high efficiency district heating scheme will replace the current system of less efficient communal boilers. Council tenants and leaseholders will still be provided with the same heating and hot water as before. The only difference will be that the heat charges to residents should be lower than those that would have been charged if the less efficient system remained in place. Q. Are local heat networks tried and tested? A. Local heat networks are clean, safe and reliable as demonstrated through Bunhill I, and used extensively all over the world, including entire cities such as Copenhagen, Stockholm, Helsinki, Berlin and Paris. Most major buildings in Manhattan, New York are connected to a heat network. In Nottingham, Sheffield and Aberdeen local heat networks provide heat to thousands of homes as well as local leisure centres, shopping centres, law courts,
commercial buildings and concert halls. There are many existing CHP plants in London, some of which are linked to local community scale heat networks. Examples include a large energy centre in Pimlico, providing heat to around 3000 houses and 40 commercial properties, and one in Tower Hamlets, which provides energy to 700 homes on the Barkantine estate as well as a nearby leisure centre and a primary school. Q. What happens if the heat network breaks down? A. Modern heat networks are designed to be failsafe. The technology is very reliable, and operation and maintenance will be carried out by an experienced and specialist organisation. They will be contractually obliged to guarantee reliability and a rapid response in the rare case of a failure. Buildings connected to the local heat network will remain connected to the mains electricity grid, and will retain back-up boilers so they are never short of an energy supply during maintenance, busy periods, or in the rare case of a failure. Q. Will there be any pollution or impact on the local air quality? A. Islington has declared itself an Air Quality Management Area due to the high levels of traffic and associated emissions in the area. This means that the council sets high requirements for new buildings to ensure that they do not have a negative impact on air quality. We will be liaising with the Council's Environmental Health team throughout the development and operation of the scheme. An air quality assessment will be undertaken to obtain planning permission. The energy centre will serve local existing buildings in the nearby area, replacing some of the heating, and therefore emissions, from their existing older and less efficient gas boilers. Q. Will the construction work and the energy centre be noisy? A. We will aim to minimise noise during construction. We will work with the contractor to try to minimise any disruption to local residents during the construction and will be talking with the local community to provide more details of the timing and works throughout the construction. The equipment within the energy centre has been designed to be installed in acoustic enclosures and once the energy centre is operational, there will not be significant noise from the energy centre. The existing local noise levels will be monitored to determine the impact of the introduction of the energy centre on current noise levels.
Q. Will there be any health risk being close to the energy centre? A. Combined heat and power systems (CHP) including Bunhill Heat and Power should not pose any health risk. CHP plants are regularly installed in hospitals, schools and new residential developments. The generation and electricity distribution at the Bunhill Energy Centre result in lower voltage levels than the London grid network and electrical substations, and is significantly lower than major power lines. Heat pumps are large electrical machinery, which will be self-contained within an enclosure, and not generally accessible by the public, therefore should also not pose any health risk. For comparison, every home has a small heat pump in the form of a refrigerator. The heat pump uses a refrigerant to operate. At Bunhill it is proposed to use a natural refrigerant (ammonia) with zero Ozone Depletion Potential, and zero Global warming potential. This refrigerant is also found in some domestic refrigerators and freezers. The refrigerant is encapsulated within the heat pump, therefore not free to escape to atmosphere. A leak detection system will be used within the heat pump enclosure to test the enclosure for any traces of ammonia refrigerant. In the event ammonia is detected within the enclosure the heat pump is immediately deactivated, made safe for further investigation and a fault reported. Q. Who will it affect and how? A. Residents who are connected to the network should benefit from lower heating bills and a highly reliable heating supply. No internal works are required although it may be appropriate to carry out other internal improvements during this period. Other public and private sector customers who will be connected to the network will also benefit from reduced heat charges. The development of the network will be timed to coincide with planned regeneration and development projects, and ensure there is no disruption to their services. The development of a borough wide heat network will provide many opportunities in the future for buildings across the borough to connect, bringing the benefits of a lower cost and lower carbon energy supply to many more people and organisations. This future expansion will provide a substantial reduction in the boroughs carbon emissions and levels of fuel poverty. The construction of the network will require laying an underground insulated pipework to connect up the various buildings to the heat network. During this period there may be some impact on roads and pavements along the route of the network. The Council will coordinate these works with the relevant authorities to ensure disruption is kept to a minimum and the public are informed of any works well in advance. It is one of the Council s objectives to minimise any charges to leaseholders arising from the installation of heat networks and it has therefore sought specialist legal advice on this matter. Clear guidance has been given that under provisions of both the Local Government Act (1976) and the Local Government Act (2000) no charges to leaseholders would be applicable. If any heat work piping or controls within estates need to be improved this would
be as part of the normal maintenance regime, and would be recoverable from leaseholders, but would not be as a consequence of this project. Q. How can I get involved? A. The Council aims to ensure community participation in the scheme wherever possible and will be exploring and promoting all opportunities for involvement as the project develops. Q. How is the Bunhill energy centre and heat network funded? A. Islington has been awarded 1.2M Euros from the EU Celsius project to be a demonstrator project for urban waste heat reclamation to other EU cities (Gothenburg, Rotterdam, Cologne and Genoa) seeking to make best use of their urban waste heat sources. Technical Information Q. How will waste heat be used? A. Heat will be taken from the tube ventilation air at around 20-30 C and passed through an air source heat pump which will turn this heat into hot water at around 80 C that can be pumped through the heat network pipes. The hot water is transported to connected building s boiler rooms and is used to heat the existing radiators and hot water systems via a plate heat exchanger. Q. Why does an electricity substation produce waste heat? A. The electricity substation takes electricity from the National Grid at 132,000 Volts and converts this to electricity at 11,000 Volts for local distribution around the streets of Islington. Although this process is very efficient (>95% efficient) there are energy losses in the process. These are in a number of forms, one is the electrical hum that may be heard from the equipment, but the predominant loss is heat arising from large electrical currents passing through wiring in the equipment at the substation, a bit like an electric kettle. As the substation is always active the heat it generates must be managed. Typically the heat is dumped to outside air using large radiators, sometimes equipped with fans. Bunhill II is seeking to recover approximately 300 kilowatts of this waste heat, equivalent to the power of 100 domestic electrical kettles. Although this sounds large, the substation will still be distributing 10-100 times more energy (Megawatts) in the form of electricity to the residents and businesses of Islington as it produces this heat.
Q. What is a Heat Pump? A. Every home has a heat pump in the form of a refrigerator or freezer. In a refrigerator, heat is taken from the air and food inside the cabinet and rejected at the back of the refrigerator using electricity. This is why the back of a refrigerator is warm. In the heat pumps proposed at Bunhill, waste heat from air is absorbed at low temperature into a refrigerant. This process is identical to that taking place inside the fridge. The refrigerant then passes through an electrically driven compressor which has the effect of raising its temperature. The heat in the high temperature refrigerant is transferred to the heat network, with cooled refrigerant returned to the air stream to be reheated and start the cycle again. This is similar to the warm air given off at the back of a refrigerator, but with the heat captured in the heat network. As only one unit of electrical energy is required in the compressor to produce 3 to 4 units of heat, the process is very efficient. Q. How does a CHP engine work? A. The existing energy centre houses tried and tested CHP technology which is commonly installed in new buildings in London and elsewhere in the UK, including new schools and hospitals. A CHP engine generates heat and electricity together. The CHP engine turns a generator, which produces electricity, whilst the heat from the engine is captured in the same way that we use heat from a car engine to keep us warm when driving. The heat from the CHP engine is distributed through the heat network to provide warmth and hot water to local
residents and buildings. CHP engines can be designed to provide heat and hot water for anything from a small house to an entire city! Q. How does a Heat Pump work? A. An air source heat pump extracts heat from the outside air in the same way that a fridge extracts heat from its inside (see what is a Heat Pump ). It can get heat from the air even when the temperature is as low as -15 C, though the temperatures of heat sources for Bunhill 2 are much higher than this. Heat pumps have some impact on the environment as they need electricity to run, but the majority of heat they produce is extracted from the air, and constantly being renewed naturally. Find out more If you would like to find out more: You can contact project manager Huw Blackwell on 0207 527 8208 You can visit www.islington.gov.uk/heatnetwork for updates on the Bunhill Heat Network and energy centre. You can find out about similar projects elsewhere in London: www.chpa.co.uk