I must admit I used to be a sceptic of the call to “electrify everything” but then that was back in the days when the carbon intensity of the UK electricity system was c.500 gCO2/kWh whereas now that intensity is down to c.250 gCO2/kWh. I also have to admit that I have been a sceptic on heat pumps and guilty of one falling foul of the ‘human” barriers to better energy management I identified back in my PhD in the early 1980s, i.e. a bias against a technology resulting from out of date experience, in this case the view that heat pumps were over-hyped and under-performing.
One of the problems with a long career in one field is that there are cycles of fashion and interest that seem to repeat, albeit with differences. Back in the early 1980s there was a push for industrial heat pumps. As is often seen in non-technical, or even semi-technical explanations of heat pumps it was said that “heat pumps are like refrigerators in reverse” (which we all know is wrong anyway as they are “running in the same direction” as refrigerators). One esteemed and highly technical expert at the time, who in fact wrote the book on industrial heat pumps which I still have on my shelves somewhere, said; “comparing heat pumps to a refrigerator is like comparing a Ferrari to a Mini. They both have four wheels and an engine but there is a huge difference in their complexity, their maintainability and their running costs”. That comment clouded my views on the enthusiasm to use heat pumps as an answer to decarbonising heat. Also, as with any technology there is no question that there were many bad installations, as always happen when there is a bubble and consumer facing hype gets ahead of installer capabilities.
My scepticism was made worse by stories like the one I reported in a blog on 28 March 2014 when the front page of the Independent on Sunday reported: “Exclusive: Renewable energy from rivers and lakes could replace gas in homes“ and the article started by saying “millions of homes across the UK could be heated using a carbon-free technology that draws energy from rivers and lakes in a revolutionary system that could reduce household bills by 20 per cent”. That piece of pure hype, which was wrong in so many ways, was aided and abetted by the then Secretary of State Ed Davey who really should have known better.
However, things change and when they do it is time to change your mind. The quote; “when the facts change, I change my mind. What do you do sir?’ is attributed to John Maynard Keynes although as with many other famous quotes apparently there is no proof he ever said it. It is clear that heat pump technology, particularly for space heating, has moved on. An article on LinkedIn by Paul Kenny of Tipperary Energy Agency, “How did the beast from the east affect heat pump performance” was very interesting as it recorded real-world performance of 16 residential heat pump installations during extreme cold weather in March 2018.
As well as advances in heat pumps the other thing that got me thinking more about electrification was some surprising data about the effects of gas cooking on indoor quality, particularly the effect on CO, CO2, NO2 and VOCs. Having grown up cooking with natural gas most of us have ignored the effects, thinking instead, if we did at all, that indoor air quality problems resulting from cooking were confined to developing countries where people cook on wood fires or kerosene stoves in poorly ventilated spaces. It turns out that we have an indoor air quality problem from cooking as well – particularly in badly ventilated kitchens. Lloyd Alter produced a good summary here. The answer is to go electric. Induction hobs are the way to go for fine control of cooking as well as improving indoor air quality.
It is clear that we are moving to a more electrified future, in heat and ultimately transport. For new build the only way to go is to mandate Passive House standard and therefore cut heat loads so much that direct electric heating (possibly with storage to allow households to take advantage of PV generated power and to interact with the electricity market) is viable. For retrofit situations where taking the building to Passive House standard is not possible technically or economically there is definitely no one silver bullet and fully electrifying the entire current heating load is clearly not going to be possible because of its impact on the electricity supply system, as Michael Liebreich pointed out, “in a normal year, the UK’s winter heating load – which is practically zero in summer months – reaches peaks six times as high as the country’s electricity load, and it can cycle up and down by a factor of three in just a few days.” Having said that heat pumps will have a growing role to play, either for individual homes or perhaps group heating schemes with thermal stores that also interact with the electricity flexibility market. Other emerging technologies such as “heat batteries” or thermal stores will also have a role to play in electrifying heat alongside heat pumps.
For more real world examples of completely electrifying homes in the harsh climate of the US mid-West check out the excellent work of Nate The House Whisperer
After finishing this blog I discovered the DryFiciency project, an EU Horizon 2020 funded project to develop high temperature industrial heat pumps with the aim of reducing specific energy for drying/dehydration/evaporation processes by 60-80%. Industrial heat pumps may yet have their day.