One year since the beginning of the war, here is our third post of the #nomoregas campaign, which aims to accelerate the transition away from gas boilers (posts 1 & 2 are here). In this post, we will analyse lesser-known alternatives to the gas boiler. To recap, we want to find solutions for the cases where installing a heat pump is not feasible or financially viable: typically flats and medium-to-small houses that will not be refurbished in the near future. The fourth post will introduce a new website dedicated to designers and homeowners who want to remove gas from their properties, so stay tuned!
Gas in the UK homes: a tough enemy..
There are 26 million gas boilers in the UK, producing more than double the CO2 of all gas powered stations in the country. [1]
{Each boiler produces} “3.54 tonnes of carbon dioxide equivalent a year, amounting to over 92 millions tonnes annually. This is over double the 41 million tonnes of emissions created by the UK’s 48 gas-fired power plants.” The plan to decarbonise relies heavily on replacing gas boilers with heat pumps, but we are installing nowhere near as many as we need. The Economist noted recently: “Of Britain’s 24.7m homes, 74% are exclusively heated by gas [2]. Home heating accounts for 14% of Britain’s total carbon emissions. The 43,000 heat-pump sales in 2021, the latest year for which full figures are available, falls far short of the rate of 600,000 per year by 2028 which the government has targeted.” And the cause might be just intrinsic to our housing stock [3]: Part of the problem is the history of Britain’s housing stock The coal burnt in Victorian-era fireplaces was replaced by “town gas”, a potentially lethal combination of carbon monoxide and hydrogen. As a result the priority was usually to build new homes that could get pollutants out rather than keep heat in. Draughts were a feature, not a bug. Heating systems were in turn designed to run hot to compensate for such poor insulation. [4]
Heat pumps have other downsides that don't make them viable in several situations. The #nomoregas research and campaign aim at easing the transition away from gas by identifying financially and practically viable alternatives to gas boilers and heat pumps.
Some alternatives to gas boilers, explained
As we can see, heat pumps are the most popular alternative to gas boilers, but not every property can be easily converted. Heat pumps require external units and may require interventions on the building fabric or the plumbing system. They are also quite expensive; even with government incentives, a fully installed system will cost in the region of £9k.
So for flats, heat pumps are often out of the question: they are too expensive, and there is no space for external units. The main barriers for small houses and garden flats are installation and adaptation costs.
In our second #nomoregas post, we introduced the concept of grid balance and how we could use the varying price of electricity to make alternative products viable. In brief: while it is difficult to preview the future of energy, we can make some assumptions based on current trends and progress in recent years. The UK is in the privileged position to de-carbonise the power grid, thanks to the abundant wind, and the government plans to do this by 2035 (whether it achieves 90% or 100% it’s not relevant to us, what this means is that electricity will become cheaper in the coming years. Cheaper electricity means that the transition away from gas boilers will not cause energy poverty; quite the opposite. It is hard to understand why this transition is not translating into homes. As renewable energy technologies become more widespread and mature, the electricity cost will decrease, making new alternatives to gas boilers accessible to everyone. Even in this positive outlook, renewables' intermittency causes imbalances on the grid, which must now deal with peaks and troughs in demand and production. The result is there are a few peak hours when the cost of electricity is extremely high and some hours at night when electricity costs are very low and sometimes negative!
A new range of products that works on a different principle has emerged in the last few years; we will call them heat batteries. Instead of producing renewable energy, heat batteries take advantage of the difference in electricity cost between day and night by charging with heat during the night and using the stored heat when needed. The result is not only cheaper electric heating and hot water, but also a big hand stabilising the grid (by drawing when there is peak offer and reducing peak demand). In other words, heat batteries are exactly what we were waiting for.
Here are the most promising product ranges that take advantage of this system.
I. Heat engines that can replace gas boilers.
II. Hot water cylinders have been around for a long time. These can be easily transformed into heat batteries, when combined with smart sensors and planning software.
Further down, we will explore systems that can integrate with smart heat batteries to expand their viability.
I. Heat engines: gas boiler replacements
ZEB by Tepeo:
The Zero Emission Boiler (ZEB) manufactured in the UK by Tepeo is the star of our investigation. It is a heat battery with a ceramic core that can be heated up to 800 C and maintains its temperature for several hours. It is a large, heavy box, the size of a washing machine, and it weighs 350kg, but once the access and weight hurdle is solved, it can be installed anywhere quite easily by most plumbers, and it doesn’t need a flue.
Zeb has an internet connection, drawings real-time information about the grid and live weather data and combines the information with the historical use of the house to take advantage of the best electricity prices throughout the day and night. Typically, it will draw most of the energy it needs during the night when electricity is cheaper and less carbon-intensive and only top up when necessary during the day.
PROS: The ZEB is compatible with a normal boiler installation. If you are refurbishing, you can run your existing gas boiler for the last couple of years to save money (windows, floor and loft insulation), but remember to reinforce the floor and verify all other compatibility aspects (see below our setup instructions).
What do you need to check:
Weight: the ZEB weighs 350kgs, so it can’t just sit anywhere. Its ideal location is on the ground floor, or if you are refurbishing the property, you can reinforce the floor where you plan on installing the ZEB for peace of mind.
Access: the weight and size also create a few problems for the installation. Very tight stairs could prove impossible to conquer.
Cost: The ZEB is not the cheapest at £6000, including VAT. It will pay itself in the long run, but it is still an investment. The government doesn’t consider energy batteries worthy of incentives; we disagree.
Maximum power: at a maximum of 12000 kWh per year, the ZEB is suitable for properties up to 120-130 square metres (unless super insulated).
Electric power load: the ZEB draws 40 amps. The typical home fuse is 70Amp, giving ample load for other items. Nonetheless, if you have a lot of other electric loads you should consider upgrading the fuse to 100 Amp.
You’ll need to switch your energy provider to one that gives discounts at night. Octopus energy, for example.
II. Smart hot water cylinders: the ideal support for alternative heat engines
I.a. Mixergy is a simple hot water cylinder with a couple of twists.
Firstly, it heats the water from the top. Hot water stays on top, so it doesn’t mix with the cold water at the bottom and stays consistently warm. This means that the heater can calibrate the hot water required and only heat that much. Second, it is smart: the tank learns your habits to be as efficient as possible. It will typically build up a reserve at night when electricity is cheapest and only reheat what you need (if you still need some) during the day.
Mixergy tank (Source: ecobubl)
Versus the traditional hot water heat battery:
Sunamp uses a phase change material. It is a heat battery in the sense that it stores heat, but it does not have the capacity or the software capabilities to take advantage of the flexible pricing. It will draw electricity when necessary. It has a capacity of to 12kWh, which typically means it can only provide hot water, but not heating.
Heat batteries and Sunamp (Source: Delta-EE)
Direct electric heating solutions
Unfortunately, heat and hot water batteries do not cover all our case studies. Each system has some limits, and almost every house is different. We propose to use direct electric backup systems to bridge the gaps and still avoid installing gas boilers. Direct electric heaters are less efficient than heat batteries discussed above, but if we design the systems properly, we only need them during the coldest days of the year. Here are two examples.
Infrared heating
Infra-red panels and fabrics. Infrared heating is different compared to the air heating we are used to. Radiators heat the air, and underfloor heating heats the floor, which heats the air; infrared heating is more akin to the winter pub heaters (without the light): you feel the heat on you, and the waves heat the objects around you. The outcome is potentially more efficient than ambient heating because it is less susceptible to loss from air movement (a draughty window, opening the entrance door, or just doors between different rooms).
The second advantage is the quick sense of comfort, which makes infrared particularly efficient in rooms used intermittently, like guest rooms, utility rooms and bedrooms. Infrared heating comes in two formats:
Panels are usually large and white and are usually installed on the ceiling. These are perfect for installing when there are no refurbishment works in sight.
A special mesh can be plastered into the ceiling and walls to become invisible. Of course, this is our favourite option when refurbishing.
Electric radiators
Our last resort solution. Electric radiators are the least efficient tool in our toolbox. Still, it has a role in the mix of gas-free solutions: to boost the heating system during the coldest days. Heating systems are designed to have enough power for the coldest days of the year. When we can’t afford the fully specified system, for cost, space or simply because there are no suitable products, we can provide backup with electric radiators.
Their main advantage is flexibility and low installation cost: they only need a socket. They can be switched on and off at will.
Their response is relatively quick.
Cons:
Inefficient and tasking for the electric fuse: each radiator draws about 4Amps, so they cannot be a complete replacement for the heating system, nor an extensive solution. But four or five radiators can go a long way on cold days.
Direct electric radiators and infrared heating are a risky bet: their success depends on the price of electricity going down. From a carbon balance point of view, we risk drawing electricity at peak time, which may be more carbon-intensive than gas. As discussed, our take on this point is that the grid will be less and less carbon intensive, and the cost of electricity will drop in the coming years. Nevertheless, should the short-term consequences of using direct electric heating be a concern, electric batteries (e.g. the Tesla Powerwall) can help us take advantage of the lower price and carbon intensity of off-peak electricity that can be deployed on demand to the electric heaters.
Conclusions: what is the best solution?
Current trends in energy supply and new products are making the transition away from gas boilers viable for almost everyone. Combined, heat pumps, heat batteries and direct electric heating systems provide a mix of solutions to cover almost any case. Navigating the myriad of cases and products can be daunting, because there is no single answer. So we have decided to create a website that helps designers and homeowners choose the right alternative to gas for their case. The website is in beta version but will be online by the end of March.
Stay tuned!