Low residential heat tariff
Improved local air quality & reduced carbon emissions
Hybrid solutions utilising both ASHPs and gas boilers
“FairHeat clearly understood the challenges that we are facing by the introduction of new technologies such as heat pumps into our schemes. The development itself was also facing major challenges with respect to rooftop space, budget and changes to apartment design, particularly at a late point in Phase One’s design. By bringing their heat network specialist knowledge and experience to the team, they were able to communicate the available options and explain the impacts, benefits and drawbacks of each to the heating & hot water team and our residents. Delivering cost effective and sustainable solutions to our tenants is of paramount importance to the business and the hybrid solution was a well thought out design that offered significant benefits in several areas, whilst still providing market leading heat network performance with a low carbon footprint. FairHeat solutions are both fit for purpose in today’s market but also future ready, with the dwelling and building systems designed to be technology agnostic. This allows us as a housing association to be confident that our developments can decarbonise over time and remain ready for policy changes far into the future.”
Head of Heating & Hot Water Services for a housing association
Background
The project development is a 950-unit new build residential development located in southwest London. The development was to be delivered in two main phases, with phases one and two consisting of 211 and 739 homes, respectively.
Challenge
The development was designed to serve heating and hot water to each property through a sitewide communal heat network. Prior to FairHeat’s involvement, Phase One had received detailed planning and Phase Two had received outline planning, with an overall Energy Strategy based on utilizing gas CHP for the low carbon baseload plant. Due to the already confirmed and anticipated changes in policy that will likely be in effect when Phase Two is submitted for detailed planning, a gas CHP solution was unlikely to either receive planning approval of meet building regulations. This is due to the reductions in the carbon intensity of the grid making the carbon offsets achieved previously with gas CHP no longer applicable. Furthermore, the original Energy Strategy had planned to contain the permanent Energy Centre in Phase Two, with a temporary boiler solution planned for Phase One until Phase Two was online.
As such, the project team was considering alternative solutions for both phases and approached FairHeat for supporting in solving three key challenges:
Could Phase One house the permanent Energy Centre for both phases, to avoid the need for an expensive temporary solution?
What was the optimal design for integrating heat pumps into the scheme, whilst working with limited rooftop space and a project budget already based on gas CHP and gas boilers?
How could ASHPs be integrated onto the heat network without requiring installing hot water cylinders in each apartment, for which there was no space in the Architect’s dwelling layouts?
FairHeat Solution
FairHeat undertook both peak and hourly load assessments for both phases of the development and reviewed the available options that would achieve compliance with the current and expected policy and building regulations governing the scheme’s planning period.
FairHeat also utilised an in-house hourly load model to analyse hour the demand would vary throughout each day, month, and year to optimise the sizing of the ASHPs, thermal stores and gas boilers. To work within the fixed constraints of Phase One’s available rooftop space, FairHeat investigated hybrid solutions utilising both ASHPs and gas boilers. To limit the total amount of ASHPs required, the use of thermal storage was assessed within the hourly load model to determine the optimum ASHP and thermal storage size whilst targeting an 85% annual heat demand fraction from the heat pumps. Gas boiler plant was then sized to provide the site’s peak demand, but only contribute a small percentage of the annual energy demand.
With an optimised plant selection, FairHeat undertook a spatial footprint assessment of an Energy Centre that could supply both Phases and demonstrated to the project team that this could be contained within the available rooftop space of Phase One. The primary driver for facilitating this overall space reduction was the use of thermal storage and peak load gas boilers to minimise the total ASHP footprint, whilst still delivering a low-carbon solution.
With an optimised plant selection, FairHeat undertook a spatial footprint assessment of an Energy Centre that could supply both Phases and demonstrated to the project team that this could be contained within the available rooftop space of Phase One. The primary driver for facilitating this overall space reduction was the use of thermal storage and peak load gas boilers to minimise the total ASHP footprint, whilst still delivering a low-carbon solution. Finally, by reducing system temperatures in the dwelling and selecting an ASHP that could operate at 60 oC, it was demonstrated that the network could supply instantaneous hot water HIUs without the need for hot water cylinders. This resulted in reducing the dwelling spatial footprint required for the heating and hot water system. It also provided a more efficient overall network, as instantaneous HIUs provide lower return temperatures than those supply hot water cylinders, which reduces network losses and reduces the risks of overheating.
Results
The hybrid solution within Phase One was able to demonstrate the following benefits to the development:
Removed the need for a temporary energy centre
Successfully integrated heat pumps in place of gas CHP without significantly increasing CAPEX or OPEX
Significantly reduced onsite combustion levels, improving local air quality and reducing carbon emissions
Removal of the dwelling hot water cylinders by specifying a system that can provide instantaneous hot water via the ASHPs
Low residential heat tariff due to the use of large thermal storage that allows the heat pumps operation to be decoupled from the instantaneous network demand
