Category Archives: Renewables

Renewable Technologies: Facts, Fiction and Current Developments

Chris Wilde, Managing Director of Yorkshire Energy Systems (YES), gave a talk Renewable Technologies: Facts, Fiction and Current Developments on 5th September 2019 at The Arkell Centre in Nailsworth, hosted by Nailsworth Climate Action Town (NCAT). The focus was on domestic renewables in UK.

Chris exploded many myths and misunderstandings that even some supporters of renewables believe in. The audience included an influential range of people, from the national political level, to district and parish councillors, from Transition Stroud, local climate groups, Severn Wye Energy Agency, and local renewable energy businesses. It was an excellent talk and very well recieved.

I will be sharing a fuller record of the talk, but to briefly summarise his words that accompanied the pictures used in the talk, using my notes …

Whereas 5 years ago, or even 6 months ago, the majority of householders installing renewables were doing it simply for financial reasons, rather than to reduce their carbon footprint, that has now changed, and about half of those now doing it are motivated by concerns about global warming. Greta Thunberg and Extinction Rebellion can take a lot of credit for raising awareness.

Chris showed an aerial view of a large 110 kW (kilowatt, a unit of ‘power’) solar PV system YES did for a company close to Wembley Stadium. What is shocking is that there are huge areas of commercial roof space without solar surrounding this installation. As Chris said, it shouldn’t be a question of seeking permission to have solar – particularly on new homes or new commercial buildings – it should be required that they do have solar, and it is much cheaper to do it at build time than to retrofit later (“solar” will be used as shorthand for solar photovoltaic (PV) in the text below):

Solar Myths

Myth 1 – Solar is ugly. Leaving aside the point that saving the planet might be seen as more important than the aesthetics of roof lines, the fact is solar panels have been getting slicker and more aesthetic. It is now possible to replace tiles completely with in-roof panels.

Myth 2 – You can only have 4kW on your house. No, you can only have 4kW per phase before seeking permission from the grid.

Myth 3 – Cannot have solar without a south facing roof. Actually, the variation in input from west or east, versus south, facing panels can be as little as 15%, and in fact having east and west facing panels can be better for households needing more energy in the morning and afternoon. On flat roofs, you can pack east and west panels more tightly (because less spacing is then required to deal with shadowing effects), and this completely compensates for not being south facing.

Myth 4 – We don’t have a roof that is not shaded, so pointless. Ok, but there are other options, such as ground mounted arrays, or a tracking system like Heliomotion (which has a UK base in Stroud). Chris also showed arrays mounted high enough for sheep to graze under; and there is even a trend now to place solar on top of parking bays. There are simply so many ways of having solar fitted, there are no excuses for not doing it!

Myth 5 – The Feed In Tarif (FIT) has ended so it cannot be made to work, financially. This is wrong on several levels.

  • Firstly, the sun’s energy is free.
  • Secondly, the price of solar has dropped while the panels have increased in output (250 to 350 kW over 5 years).
  • Thirdly, it is true that FIT gave householders 40p per kWh (kiloWatt hour, a unit of ‘energy’) for all energy generated, whether exported to the grid or not, and an extra 3p per kWh for 50% of that generated that is assumed to be exported to the grid. However, while there are now no FIT payments, utility companies will have to pay for what you export, under the new Export Guarantee Scheme (Octopus are already offering 5.5p per kWh even before the scheme comes in).
  • Fourthly, with a low cost ‘solar diversion switch’ any excess solar energy can be used to heat hot water, avoiding the need to export it to the grid (and by the way, this simple device has essentially killed the ‘solar thermal’ market).
  • Fifthly, systems that were costing between £3,000 and £4,000 per kW are now down to £1,000. So, in short, payback of a solar system is still possible within 6-7 years even without the FIT subsidy.
  • Finally, the reduction in bureaucracy with the loss of FIT means that it actually might, paradoxically, accelerate uptake of solar.

Heat Pump Myths

Chris started by explaining how heat pumps work, which seems miraculous to many people, but is the product of 17th century physics: if you compress a gas, it gets hotter. And a heat pump works by transferring heat from the air (or ground) via a fluid (a refrigerant) that is compressed and then releases its heat inside the building. But for each unit of energy used by the pump, 3 to 4 units of energy is extracted from the air in the form of heat. The two main categories of heat pump are Air Sourced Heat Pumps (ASHP) and Ground Sourced Heat Pumps (GSHP). The efficiency of a heat pump will vary with external temperature, but overall is quoted as a seasonally averaged figure.

Assume you had an ASHP with 3.5 efficiency factor. If you have a heating requirement of 18,000 kWh for your home, this could be achieved by using 18,000/3.5 = 5,143 kWh of electricity. Mains gas is currently 3p per kWh and mains electricity is 13 p per kWh so to heat the house with gas would be 18,000 x £0.03 = £540 per year, whereas to do it with this ASHP would be 5,143 x £0.13 = £669; still a bit more than gas, because gas is currently ridiculously cheap, but a few things to consider:

  • when a crisis occurs in the Middle East for example, gas prices can rise, and don’t have to swing much to wipe out the current distorted advantage of cheap gas;
  • a tax on carbon including gas, will come sooner or later to reflect the damage that carbon dioxide emissions are doing;
  • even if today some electricity is coming from fossil fuel plants, increasingly the grid is being ‘greened up’ (see www.carbonintensity.org to look at how much the grid has already greened);
  • as you will see below, if you add solar to a heat pump the maths flips, because you can use the free solar electricity to help drive the heat pump and even if that is not all year round, 24-7, it has made a huge difference;
  • finally, if you cannot add solar to your heat pump for some reason, many people are prepared to pay an extra £100 or so per year to save the planet (that is clear from the recent boost in heat pump installations YES have been seeing).

One other key point is that heating a house using a heat pump requires sufficiently large radiators because it operates using a flow temperature of 45/50oC, rather than say 70oC as with a gas boiler. At 45/50oC they still heat the house to the required temperature (typically 21oC), but does so with a larger surface area of ‘emitter’ (this effectively means a slight fatter radiator, and depending on how old the heating system in a house is, that may mean that some of the radiators need to be upgraded, but rarely all radiators; even better, under floor heating can be used, increasing the area even more).

Myth 6 – It cannot work when it is cold outside. Yes it can, as described. It is basic physics at work, and no magic is involved!

Myth 7 – They are more expensive than a gas boiler, so are unaffordable. Heat pumps are more expensive to fit but the Renewable Heat Incentive (RHI) was designed precisely to deal with this. It is paid to the householder over 7 years (and commercially over 20 years), reducing running costs and overall, paying off half to two-thirds of the cost of the installation. To qualify for RHI, the key requirement is roof insulation, and if you have cavity walls, then cavity wall insulation.

Myth 8 – They cannot work in old leaky houses. Untrue. Chris presented an example of an old rectory with 290 square metre floor area, that had good roof insulation but with walls that could not be clad, and overall it was a high heat loss building. It cost £3,500 per year using an oil boiler to heat it. Using a brilliantly effective combination of a 10kW solar array and 6 under lawn ‘slinkies’ to feed a GSHP, the heating bill dropped to £1,500 per year.
That is despite the heating system being set to ‘on’ all the time (but obviously, with a thermostat it runs only when the temperature drops below the required temperature). The 80 year old grand mother loves visiting the house now because “it is always so cosy”. Chris is not saying, from this experience, that insulation is unimportant – it is crucial you get good insulation – but where it is not up to modern standards, don’t let that be a reason for not installing renewable heat: That is, a heat pump with or without solar, but preferably with because the solar reduces the amount of electricity used from the grid, and swings the maths in favour of heat pumps (versus gas).

Chris gave another example of a bungalow (177 square metre floor area) that was costing £1,551 per year to heat. With just a 4 kW roof mounted system and a 14 kW ASHP the bill came down to £903. Now this was £168 more saving than they had expected. Why? Chris believes this is down to behavioural change. Instead of the behaviour with traditional gas systems which can heat up a house fast, and people switch up the system when cold and down when hot – creating a see-saw effect – with heat pump systems, people can just keep it on and be comfy at a sensible temperature (whichever is their preference). Increasingly, Chris is persuading householders to refrain from fiddling with the heat controls and allow the system to work as pre-programmed and provide consistent, comfortable but not hotter than required levels of heating. This changes behaviour and actually creates a perception of a cosier home and reduced bills; what is not to like?

The caveat is that we need more skilled fitters who do not put in the wrong sized radiators, or pipe work, and of course householders who don’t leave doors open (trying to heat your local town is not a sensible approach!).

Renewable technologies like solar and heat pumps are not rocket science, but a basic knowledge is required and vendors are very good at providing training. Along with persuading householders to take the plunge we also need to transfer trade skill sets, to acquire the knowledge and experience to help increase adoption. If your plumber says they don’t know anything about heat pumps, encourage them to take a course – to unlearn some old ways and learn some new ways – and they might be in the vanguard of the change to renewable heat in your neighbourhood.

Chris also mentioned that he has found an issue related to Energy Performance Certificates (EPCs). The question Chris is asking Government is this:

Why is it that it is government policy to encourage the installation of heat pumps through the Renewable Heat Incentive scheme, yet EPCs never recommend them and even discourage them by predicting higher running costs for heat pumps even than old oil boilers contrary to the research carried out by the government in 2013 on which the RHI was based? Does the left hand not know what the right hand is doing?

Chris has written a paper EPCs: A MAJOR OBSTACLE TO HEAT PUMPS AND DECARBONISATION going into more detail on this issue, that can be found on the YES website.

Chris covered a number of other points and new developments such as thermal storage, but I hope this summary does justice to what was an excellent and inspiring talk.

We have a climate emergency – we need to start behaving like we actually believe it!

So let’s get to work, and make it happen! There is no excuse for not doing so.

This summary of Chris Wilde’s talk is based on my notes, so will be incomplete, as Chris is a brilliant speaker who doesn’t need a script or use bullet points. So, if any errors have crept in, naturally they are mine. Richard Erskine, 7th Sept. 2019. Any comments please provide via my blog.

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