CHP & DISTRICT HEATING


Left, low carbon heating is being provided to housing estates in Southwark


Below, the heat pumps supply heat at 75°C, which enabled residents to continue to use existing heat emitters


replace heating circuits and emitters. Despite their higher supply


temperature, the heat pumps are still relatively efficient and supply 2.9 times as much heat energy as the units consume in electrical energy. Algorithms incorporated into


the systems controls optimise the operation of the heat pumps, including taking advantage of demand side management on the electrical supply. This will ensure the heat pumps top up the system when there is surplus grid electricity and grid electricity prices are cheaper. Heat pump operation will be inhibited, where this can be achieved without compromising the heating requirements of the homes, when grid electricity prices are high.


Retrofitting heat pumps to decarbonise district heating


Anastasia Mylona


Technical director of CIBSE


www.cibse.org H


eat pumps are being used to upgrade the district heating systems on three housing estates in South London,


helping the Borough of Southwark reduce its CO₂ emissions by an estimated 1,774 tonnes per annum. This innovative project has been


recognised by the Chartered Institution of Building Services Engineers (CIBSE) as a demonstration of how existing heat networks can be upgraded using engineering expertise and innovative technology. The project was shortlisted in the Residential Category of this year’s CIBSE Building Performance Awards in recognition of the actual, measured performance outcomes and carbon savings delivered. Originally, the local heat networks


serving Consort, Newington and Wyndham estates were supplied with heat from gas-fired boilers. Now, the three local heat networks have been upgraded with the installation of five purpose-developed water source heat pumps. Two 600kW heat pumps have been installed in the plantrooms at both Newington and Wyndham estates while a single 1,000kW unit serves the Consort estate. J&E Hall and iCAX worked closely with the Environment Agency to develop the scheme. Using boreholes, the heat


26


pumps extract low-grade heat from the groundwater trapped in the chalk aquifer 120m beneath and upgrade it to 75ºC to enable it to heat over 2,000 homes. The cooled groundwater is then returned to the aquifer. This has the added benefit of helping cool the aquifer, the temperature of which has been steadily increasing.


Heat pump installation The existing gas-fired boilers were retained to add resilience to the heat pump system and provide top up heat, if required, on the coldest winter days. Laser scanning to produce 3D images were used to establish the space


Heat from groundwater trapped in the chalk aquifer beneath London is being used to decarbonise three South London housing estates. Anastasia Mylona explains how the project succeeded in cutting carbon emissions while avoiding disruption to residents.


available for the heat pump installation in the estates’ already congested plantrooms and to enable the designers to establish pipe routes to allow the new heat pumps to connect into the existing heating distribution pipework. The five water source heat pumps


were developed by J&E Hall in conjunction with iCAX to supply water at 75ºC. At this higher water temperature the heat pumps are able to connect directly to the estates’ existing heating systems. This enables the heat pumps to provide heated water at a similar temperature to that from the gas-fired boilers and avoids the need to


Advice on the design of heat pumps and district heating systems


Heat pumps are the most efficient way to generate heat from electricity. They have a crucial role to play in the transition to net zero, particularly in the residential sector. To help designers deal with the design and optimisation of heat pump systems, CIBSE has issued the following publications: Application Manual (AM) 16 heat pump installations for multi-unit


residential buildings This document deals predominantly with the design and optimisation of heat pump systems. It covers the full life cycle, including installation, commissioning, operation, maintenance and decommissioning. CIBSE AM17: heat pumps for large non-domestic buildings provides


and consolidates best practice guidance with the aim of supporting high quality design, installation, commissioning, operation and maintenance of large heat pump systems. The Institution has also published two codes of practice relevant to this


scheme: CP1: Heat networks: Code of Practice for the UK and CP3: Open- loop groundwater source heat pumps. Both publications cover all stages of a project from initial brief to end of life and disposal. Each Code of Practice has an introductory section outlining scope, key legislation and typical applications and recommends best practice for systems. The codes provide clarity of responsibilities across the supply chain and measurable minimum standards, making them relevant to clients and developers as well as engineering specialists.


Financial matters Funding for the project was from a £7 million low interest loan from the Mayor of London’s Energy Efficiency Fund. This is being repaid with income from the government’s non-domestic Renewable Heat Incentive (RHI), which was secured by the council for 20 years. Without the RHI, the project would not have worked financially because the cost of input electrical energy remains higher than the previous cost of gas consumption. The Mayor’s funding meant


residents did not have to contribute towards the capital cost of the scheme, so there has been no increase to them in the cost of heating as a result of decarbonising the local district heat networks. The RHI is now closed to new applications so registered social landlords looking to implement similar schemes will need to find other sources of funding – at least until the price of electricity drops significantly relative to the cost of gas. Following the scheme’s successful installation, in 2022 the London Borough of Southwark implemented a five-year maintenance package to optimise the systems’ operation and maximise efficiency in operation. The decarbonisation project was


a key part of the London Borough of Southwark’s climate strategy and action plan, where 75% of the borough’s carbon emissions are from buildings. In addition to reducing carbon emissions, by minimising the need to burn gas the scheme has also improved local air quality by reducing harmful nitrogen oxide emissions. And while it is true that some CO₂ will be released by power stations in generating electricity to power the heat pumps, the increased use of renewables means that the carbon attributed to the electrical grid will continue to fall into the future – all of which show why the scheme was worthy of inclusion on the CIBSE BPA shortlist. ■


EIBI | JULY � AUGUST 2024


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36