If you were planning to move, build, or renovate your house and were given a choice of what fuel to use for your central heating and hot water demand what would you choose – air source heat pump, ground source, natural gas, oil, or biomass?
There is a wide range of heating solutions on the market and the recent energy price ‘spike’ has made consumers more energy aware as we look to a net zero carbon future.
But what option is realistic and affordable in today’s world?
As NI looks forward to a heat consultation in the summer months, many pundits are suggesting we need a range of technologies and that all low-carbon pathways should be explored.
In GB and the Republic of Ireland, both governments are proposing an all-electric future with Air Source Heat Pumps (ASHP) being promoted as the preferred option, with district heating in urban areas.
In this author’s opinion, an ASHP is an ideal product for a new build or thermally efficient house but with 70% of bungalows, 50% of semis, 53% of detached and 44% of terraces in Northern Ireland being in SAP Band D – G, the question remains, “will these houses be suitable for a heat pump?”
Many will claim yes, but with Governments’ own data showing that to retrofit/upgrade insulation and install a heat pump will cost anywhere from £23K to £30K and, with consumer finance at a real time low, is this really a viable option for the c.500,000 homes currently using oil and c.200,000 using natural gas in Northern Ireland?
CO2 equivalent emissions reduced by up to 90%
One consumer in Ballyfrenis, Millisle, believes that low-carbon liquid fuels and off-peak battery storage is the answer. They have taken the plunge and converted their new liquid fuel boiler to run on a renewable liquid biofuel called Hydrotreated Vegetable Oil (HVO).
The solution was designed by Next Gen Power, and London-based Green Biofuels Ltd. (GBF) supplied the advanced HVO fuel, called GD+, which is made from renewable waste cooking oil and reduces CO2 equivalent emissions by up to 90%.
As part of the project, the hot water is hydraulically separated from space heating and is supplied by a solar assisted heat pump. This allows the boiler to operate in condensing mode all the time. In addition, the client has added 4.5kW of solar PV linked to battery storage in the garage. He charges the battery pack overnight. Any excess is exported back to the grid.
The new homes in Ballyfrenis were completed in 2022 and are built to a good energy efficient specification. A biofuel ready condensing boiler was already in place and air permeability is 6.7 m³/h.m², which is average. The EPC on completion was B86, which is very good but that was before the fuel change and the addition of solar.
So how carbon ‘friendly’ is this house?
We have modelled the emissions on kerosene and grid electricity and, for the purposes of this exercise, we have assumed a space heating demand of 9,000 kWh, a hot water demand of 3,000kWh and a further 6,000kWh of general electric use. This gives a projected annual carbon emission total of c. 6.3 tonnes. This is made up of 4.5 tonnes for the space heating, 1.125 tonnes for hot water and 1.80 tonnes from the grid.
When we model using HVO for the space heating we can reduce the carbon emissions to 0.48 tonnes per annum. With the hot water being provided by the solar assisted heat pump, the emissions reduce to c.0.18 tonnes.
For general electrical requirements and utilising the 4.5 kW solar PV generation and an assumed load factor of 0.1 we can assume approx. 4,000 kWh from solar over the year, leaving a 2,000 kWH requirement from the grid. This results in c.0.6 tonnes of CO2 from general electric use.
OFTEC oversaw the boiler conversion and the project is being monitored by Dr Patrick Keatley of NEMO Energy Limited. Looking at the figures he commented: “With HVO emitting 0.036 kgCO2/kWh compared to kerosene at 0.298 kgCO2/kWh, we can achieve a substantial reduction in the carbon footprint immediately.
An effective decarbonisation solution
Adding in the benefits of the solar assisted heat pump for hot water, along with battery storage, we are estimating that we can bring the carbon emissions down to 1.14 tonnes of CO2 which is almost 90% lower than the original footprint using kerosene and 100% grid electricity. We will be monitoring the property over the next 12 months and will confirm the findings at the end of the year.”
The revised EPC (incorporating the fuel change and solar) moves from a B85 rating to an A96 which is extremely high. For reference, the average energy rating in Northern Ireland is D60.
In terms of CO2 emissions, an HVO-fired boiler can deliver the most rapid and significant reductions and requires the least behavioural change by customers. While there are challenges around cost and supply at scale, it is clear that HVO could be an effective decarbonisation solution for energy efficient, liquid fuelled homes in the future.
Government support for HVO as a low-carbon heating solution could make it a relatively straightforward and cost-effective option for decarbonising liquid fuelled homes today.
