Apparently, heat pumps are going to be the saving of UK energy crisis, that and renewables but I don’t think with the current technology this is realistic as they have a number of challenges. This is a technology that Fortune recently noted came to prominence in the 1970s when the US suffered an energy crisis but that has largely been ignored once the cost of oil retreated (the article uses a photo from Viessmann heat pump assembly line). Basically, a heat pump operates in the opposite way to an air conditioning unit sucking heat out of the air and using it to heat air or water. It relies on electricity to do this and as the cost of electricity is significantly higher than gas, still the order of 400% so the efficiency of these units is critically important.
The first challenge is the need for a low operating temperature of the order of 35 to 45 degrees in order to ensure an appropriate level of energy efficiency as this is critically important as noted above. The energy efficiency is referred to as the SCOP (seasonal coefficient of performance) which takes into account the seasonal variation of the ambient air temperature. Related to this is the fact that the operating temperature is so low you need a separate hot water circuit if you used a storage system as the water needs to be around 60 degrees to avoid legionella bacteria which causes legionnaire disease (see HSE link) and the water should be distributed at around 50 degrees.
The low operating temperature means that you have to resize the radiators to achieve a similar level of warmth in your house. This is not straightforward and it is highly likely that you will be required to replace the majority of your radiators so installation can be both time-consuming and expensive.
One of the other challenges is that the current generation of heat pumps uses fans therefore they are noisy and they only have a 10-year life expectancy. The noise can be an issue with regard to placement, particularly with regard to your neighbors, and the 10-year issue means that you need to ensure that the efficiency of the system is optimised so that it does pay for itself after all the primary reason for installing a heat pump is to reduce your energy costs.
What we need are heat pumps that offer:
- Offer higher operating temperatures to simply installation
- Have efficiencies of 400% to 500% or better so they are cost-effective
- With a longer life expectancy to offset the higher initial outlay
- And are silent or near silent
This is where the new generation of thermal acoustic heat pumps comes in. They offer higher operating temperatures, good efficiency, a life expectancy of 15 to 20+ years and are nearly silent. The other thing they offer is the ability to reverse the cycle so they can be used for cooling in addition to heating, btw the Space Shuttle Discovery had a thermoacoustic refrigeration device. Although a ground heat pump can offer this it requires the order of 70m2 of ground and therefore most domestic heat pumps will use air as the source or sink.
These new heat pumps have been in development for over the last decade and are now becoming a commercial reality with Dutch and French companies looking at bringing them to market in the next year. Blue Heart Energy is looking at running pilots in 2022 while Equium is looking at introducing its first product this year.
Have a look at the following video — Introduction to Blue Heart
We are seeing some additional development in phase-change thermoacoustic heat pumps with a headline in the New Scientist that this technology along with paper strips (what are cellulose paper strips) will offer three times the efficiency of existing technology (greater than 40% of the Carnot limit) but when you look at the details the temperature differential needs to be 90 degrees. This means that this technology is not going to be applicable to consumers but may have use in industrial applications.
I installed one of the first Viessmann condensing boilers some 20 years ago and it still going today, justifying the initial outlay. I am hoping it will last another couple of years until this new generation of heat pumps becomes available.
It is worth noting that high-temperature heat pumps are coming to market that are largely drop-in replacements for existing gas boilers such as the innovative Vattenfall/Feenstra one but it does require 1.5m2 of floor space and has a weight of 300kg which will limit its deployment.
- Climate change and the energy crisis are powering the comeback of a 1970s technology now being installed in 40% of new U.S. homes
- EQUIUM Acoustic Heat Pumps
- Blue Heart Energy
- A standing-wave, phase-change thermoacoustic engine: Experiments and model projections
- Managing legionella in hot and cold water systems
- Meet the man who might have solved the UK’s heating problem