What the path to net zero will look like

Martyn Bridges discusses the alternative technologies to hydrogen and heat pumps which can contribute to net zero 2050.

Preparations for net zero 2050 are well and truly underway. Having spoken a lot about how hydrogen solutions and heat pumps will contribute to decarbonisation, it is worth turning the conversation to the alternative technologies set to play equally crucial roles. These technologies include bio-oil -fired boilers and Heat Interface Units (HIUs). While somewhat overshadowed in conversations surrounding decarbonisation, each one can offer crucial solutions in the bid for net zero.

So, how can we use each of these technologies and how are they best situated for decarbonisation?

Oil boilers

Oil boilers will not be familiar to the majority – in the UK, some 23 million homes have a gas-fired central heating system, while only 1.2-1.3 million have oil-fired heating. They are a minority in comparison, but from an urgency perspective, targets concerning oil-fired boilers are the first BEIS have in their sights. It is rare to see oil boilers being installed into new build properties, as it is difficult to achieve the emission ratings in such properties. They are mostly found in the 1.2-1.3 million existing homes that are off the gas grid. These homes are mainly in remote areas where gas is not available and in old properties or even listed ones which are difficult to insulate or renovate. To substitute oil with anything other than oil is a tough challenge. The government is currently hoping that heat pumps will be the technology to save the day here – in fact, a new scheme will come into operation on 1st April 2022, offering a £4,000 upfront payment to consumers to swap an oil boiler for an air-to-water heat pump. Whilst the new scheme is encouraging, it is somewhat limited in detail. As many homes will need some fabric upgrades and changes made to the radiators and pipework. Consequently, the £4,000 may not make much of an inroad to the actual costs required for the change.

Did you know?

Oil heating systems can be decarbonised with a high blend of HVO rather than having the entire heating system swapped out for the only other alternative on the table.

Alternatively, you can 'green' the oil, using an alternative such as HVO (hydrogenated vegetable oil). OFTEC have been running a series of trials in recent months, where around 20 homes have been running on HVO. The trials are taking place with existing boiler installations and demonstrate that HVO is very much a 'drop-in fuel' that requires little or no change to the installation and the house.

We are optimistic that BEIS and the government will consider such alternatives alongside electric heating. Perhaps by greening the oil to a 100% or lower blend, while supplementing these lower blends with low emission technology such as an air-towater heat pump and solar water heating. As such, oil heating systems can be decarbonised with a high blend of HVO rather than having the entire heating system swapped out for the only other alternative on the table.

Heat Interface Units (HIUs)

HIUs look similar to boilers. But, there is no flue or gas supply, as they take heat from a central tank or calorifier, store the heated water ready for domestic use and distribute this into the apartments or houses where they are sited. Therefore, they are technology or fuel agnostic; it does not matter where the hot water comes from or how it gets hot. In different schemes, the hot primary water feeding the HIUs comes from heat pumps, waste industrial heat or biomass boilers. The majority, though, are still using heated water generated from gas-fired boilers. Consequently, they are not (and will not be) low carbon until the gas is decarbonised with perhaps hydrogen gas. There have been some creative solutions to this, particularly in London where large amounts of high-density housing and tower blocks have their hot water tanks heated using heat from the underground tube network via a heat pump. In Wakefield, a 3,000 litre calorifier is heated by a biomass boiler to provide hot water to a social housing site of around 120 homes. Whilst the lead boiler is a biomass boiler, there is a gas-fired boiler to provide back-up in case of servicing or breakdowns. The government has, in my opinion, a perhaps over-ambitious belief that HIUs will be used on a wide scale in such housing sites, as the disruption caused will make this difficult.

However, in tower blocks and apartments that are brand new, it makes sense to use the technology. The investment is high, but it is worthwhile. Using heat pumps, solar thermal or even hydrogen to heat these tanks offers a great solution for these high-density housing situations. In summary, while conversations surrounding decarbonisation tend to focus on hydrogen solutions and heat pumps, other technologies have a lot to offer on the road to net zero 2050. ■