With UK government making a clear commitment to the rapid decarbonisation of heat with the introduction of a future homes standard mandating the end of fossil-fuel heating systems in all new build homes from 2025, self-builders are in a prime position to lead the way by incorporating eco-friendly building techniques and innovations in renewable technology into their projects.
In an effort to reduce pollution and improve air quality, the Committee for Climate Change (CCC) recommends homes should make use of low-carbon sources of heating, in particular electrically-powered heat pumps that produce no point of use emissions. Widespread growth of this technology is therefore anticipated, but what impact will this have on the national grid and how can self-builders get the best efficiencies from this technology at the lowest cost possible? James Standley, Managing Director of Kensa Heat Pumps, investigates in this article.
Reducing the impact on the national grid
The widespread adoption of heat pumps across the UK will increase electrical demand and concerns have been expressed that this will unduly increase the strain on the grid beyond its capacity, particularly at peak times. However, self-builders should be reassured that ground source heat pumps produce up to three times more energy than they consume and therefore actually reduce the load imposed on the grid. For every 1kWh of energy a ground source heat pump uses to power itself, you will typically get 3kWh of energy to heat your property.
Recent research confirms that the electrification of domestic heating on the grid is far less problematic than many had assumed. A paper published in the international peer-reviewed journal, Energy Policy examining the impact of large scale deployment of heat pumps on national demand concluded peak heat demand is 170 GW, around 40% lower than previously thought, and the maximum ramp rate is 60 GW/h, around 50% lower than previously thought. The report says that ‘a shift towards heating GB’s homes using electricity rather than natural gas will therefore put much less pressure on the electricity supply system than previously anticipated’.
Smart controls, load shifting and energy storage
In addition, the emergence of dynamic tariffs (which vary electricity charges depending upon the time of use), heat storage products, smart-controls and, in some circumstances, battery storage, will not only mitigate capacity problems, but actually have a positive effect on the grid, further enhancing the carbon benefits and cost savings for savvy self-builders.
By using smart controls that learn the occupant’s preferences and building heat physics, it is possible to avoid the peaks of grid strain and shift load to the times when the grid can best accommodate it, and there is lower carbon and lower cost electricity. This means that the heat pump will turn on when there is extra capacity and turn off when the grid is under strain.
Ground source heat pumps have far more potential to participate in load shifting initiatives than air source variants, as the ground is a very stable temperature heat source. This means a ground source heat pump can be run at the same efficiency any time of day or night (unlike air source where the efficiency is lower when the outside air temperature is colder at night).
The grid generally has most excess capacity overnight and some of the variable tariffs go negative some nights, so people could actually get paid for running their heating. If you combine some energy storage local to the heat pump, it is possible to even further reduce the peak demand.
In one project that Kensa has recently been involved with, self-builder Owen Stinchcombe built an inspirational energy efficient house in rural Gloucester, featuring Solar PV and ground source heat pump technology, operated by innovative smart controls and linked to a battery storage system.
The 6kW Solar PV array on the roof generates electricity which Owen can feed back into the grid to generate a profit via the Feed-In-Tariff. Any excess is stored in the battery and then used to power the 15kW Kensa Hybrid ground source heat pump which provides heating and hot water to his home when the electricity tariffs are at their lowest.
Heat pumps in retrofit projects
It is not only self-build properties that can benefit from ground source heat pump technology; retrofit projects can also enjoy lower carbon emissions and running costs compared to fossil fuel technologies.
A concern about the widespread roll-out of heat pumps into existing properties is the misconception that they won’t operate effectively without the high levels of fabric efficiency that you would expect to see in a new-build, for example with an EPC band of C or better, and underfloor heating throughout. In fact, the vast majority of Kensa’s very successful large-scale ground source heat pump retrofit works are in properties with an EPC of D or lower!
And Delta-E, in its December 2018 study into the ‘Technical Feasibility of Electric Heating in Rural Off-Gas Grid Dwellings’, reported that ‘based on average peak winter day temperatures, around 84% of homes can be electrified at their current level of insulation. This increases to around 93% if all suitable homes have loft & wall insulation installed’.
Obviously not all retrofit buildings can be as well insulated as a new build, especially in the case of barn conversions or where a property is listed or historic. However, what isn’t widely understood, is that improving insulation in a property containing a ground source heat pump typically results in a ‘double-win’ in comparison to a boiler, for example.
Extra insulation reduces the amount of energy required to heat a building, and means that this energy can be delivered at a lower flow temperature, because the emitters need to emit less heat. This actually improves the efficiency of a ground source heat pump – by roughly 2% for every 1*C reduction – and a more efficient heat pump will result in lower running costs.
One such retrofit project in rural Somerset involved a Kensa 15kW Hybrid ground source heat pump combined with a Solar PV system installed into a converted barn called Orchard House. As the barn was converted in the mid-2000’s to current building specifications, the heat pump was integrated with the barn’s existing heating system of radiators and underfloor heating to provide efficient space heating and sufficient hot water temperatures, covering 100% of the property’s requirement.
The 6kW solar PV array on the roof of the barn provides the customer with further self-sufficiency; generating electricity throughout the day, supplementing the electrical use of the ground source heat pump and providing an additional source of income through the Feed-in-Tariff.