Category Archives: Renewables

Small Is Beautiful – local renewables and storage can catalyse the greening of grid

Governments of all shades, and energy utilities, tend to believe that large, centralised solutions are the most cost-effective because of the economies of scale. There is a belief  that local solutions will increase costs. 

Ground-breaking work by an energy modelling company in the USA (Vibrant Clean Energy (VCE)) has turned this argument on its head, and this could, or should, have profound implications for any strategy to decarbonise the power grid in any country, including the UK, with renewables playing a dominant role in the future.

VCE summarise some key conclusions:

The present study finds that by including the co-optimization of the distribution system, the contiguous United States could spend $473 billion less on cleaning the electricity system by 95% by 2050 and add over 8 million new jobs. … The findings suggest that local solar and storage can amplify utility-scale wind and solar as well as provide economic stimulus to all regions across the contiguous US.

The study finds that wind, solar, storage and transmission can be complements to each other to help reduce the cost to decarbonize the electricity system. Transmission provides spatial diversity, storage provides temporal diversity, and the wind and solar provide the low-cost, emission-free generation.

We understand that what is true for USA can be true of the UK. 

Now, in the UK, various groups have already published reports based on modelling of the grid to show that net zero is achievable. The Centre for Alternative Technology (CAT) produced a report ‘Zero Carbon Britain – rising to the climate emergency’ that showed how this could be achieved. They used granular weather data to help model supply and demand at national scale. Energy storage was included at utility scale (using excess energy on windy/ sunny days to produce synthetic gas that could be used to generate electricity during periods when both wind and solar were too low to meet total demand).

VCE have gone much further in the sophistication and granularity of the modelling:

  • Firstly, they have modelled the dynamical behaviour of the grid at all scales – with 5 minute intervals and 3km square spatial grid over a minimum of 3 calendar year (and for planning reserves up to 175 years hourly at 30km grid). There was always a suspicion with other models that even if the national supply and demand appear to match up at a point in time, the grid will experience issues at particular points in the grid, particularly at local pressure points. VCE have addressed these weaknesses.
  • Secondly, the economics of how the roll-out of the capacity is achieved is key to policy. The modelling includes economic aspects to show the marginal cost of each new tranche of generating capacity; and so modelling the evolution of the network, not just an assumed end point. VCE have modelled the period between ‘now’ and future end dates to see what impact different scenarios have on the marginal and net costs. 

The astonishing result that VCE have found is that local renewables with local storage – even at only 10% of the total generating capacity – make a disproportionate impact on the speed and cost of further roll out of associated utility scale renewables. This is because it creates flexibility in the grid and relieves pressure points.

VCE note that this was an emergent behaviour of the system, which the modelling revealed, and certainly not obvious to energy specialists, because its only emerges when the model reaches a sufficient level of sophistication. 

The bottom line is that we should see local renewables (including community energy schemes) not as marginal additional capacity in the transition to a greening of the grid, but as a key ingredient to both speed up – and lower the cost of – the transition. We should see small and big as beautiful, working collaboratively, to accelerate the greening of the grid.

This may seem quite a technical point for those who are not students of the energy system, but it is truly remarkable and transformative, and from a policy perspective, it highlights the need for Governments to continue to promote and invest in large, utility scale renewables, but also to assist in the roll out of local renewables and associated storage.

UK Treasury, please take note!


“Why Local Solar For All Costs Less: A New Roadmap for the Lowest Cost Grid”, Vibrant Clean Energy (VCE), December 2020, 


VCE define emergent behaviour as follows:

Emergent behavior is characterized by properties and behavior that is not dependent on individual components, but rather the complex interactions and relationships between those individual components. Therefore, it cannot be fully predicted by simply observing or evaluating the individual components in isolation.


Filed under Renewables, Transition to Low Carbon

The Green Electrification Sceptic

I have had a number of conversations over the last few years with friends and associates working in climate and green groups who are sceptical about the focus on electrification in decarbonising our energy. They are, for want of a better phrase, green electrification sceptics. 

They will argue that only massive reductions in the consumption of energy is the way forward, while of course they agree that we should stop using fossil fuels and are not opposed to electrification per se.

They are neither climate deniers nor renewables deniers (those two being birds of a feather). But they do represent a significant strand of opinion that believes the UK electricity grid won’t be able to cope, within the required timescale, with the demands of transport (Electric Vehicles) and heating homes (using Heat Pumps), because of the huge amount of energy we currently use nationally in the form of gasoline and natural gas.

They would instead argue for a modal shift towards walking and cycling, and public transport and – for many homes – deep retrofit. This should be the focus they would argue, instead of trying to do the same things we do today – with all the wasted energy that involves – and try to decarbonise that.

Well, I agree with this sentiment. 

Driving a few miles to a shop to get a loaf of bread when we could have walked or cycled; heating our homes with gas boilers with upstairs windows half open; and all this with no price paid for the damage done by our carbon emissions.

It’s crazy and I agree with that.

However, people do need to move around, and for some in rural areas at least cars are unavoidable, even with improved public services. We certainly should not need 30 million cars in the UK in 2050 or even 2030, but zero is also not the right answer. And we need to heat our homes in winter, and we are not going to apply PassivHaus levels of retrofit to the (according to BRE) 9 million ‘hard to treat’ homes in the UK – at least on that timescale. We need a plan, and the numbers that back up the plan must have a sound basis.

This is where I want to challenge green electrification sceptics, because I see a tendency to bolster their arguments with information that doesn’t stack up. This helps no one, because it doesn’t get us to a realistic plan we can all work towards. And we need to scale up whatever we do pretty damn quick, with solutions that we already have to hand (techno-futurism is a tactic used by the denialists to delay action, and we shouldn’t fall for it).

A Typical Argument

The following figure is from the July 2017 issue of Energy Consumption In the UK from BEIS, and used for illustrative purposes only. 

BEIS 2016 energy equivalents

Electricity in 2016 was about 20,000 ktoe (Kilotonnes of oil equivalent – a unit of energy) and (natural) gas plus petroleum was about 150,000 ktoe. 

So, the argument goes, we’d need to increase the electricity energy generated by at least 7 times to displace the gas and petroleum, and this doesn’t sound feasible by 2050 let alone 2030 (the date that many local authorities in UK are committing to getting to net zero in these sectors). 

My Response

The basic issue here is confusing primary energy, shown on this graph, with delivered energy, and this overstates the amount of electricity that would need to be generated to displace the fossil fuels shown.

‘Primary energy equivalents’ includes not only the delivered energy, but any energy lost as part of the transformation from one form (e.g. gas) to another form (e.g. electricity) of energy. 

But there are other factors to take into account when considering the feasibility of electrifying transport and heat. I have listed them here, and they fundamentally change the basis for any debate regarding the electrification  of transport and heat in the next few decades:

  1. Primary energy equivalents: For fossil fuels these shouldn’t be used as measures of the energy required in a transformed system, without appropriate adjustments.
  2. End-Use efficiency factors: Inefficiencies of internal combustion engine (30% efficient) compared to a EV (90% efficient); see Note 1.  Heat Pump (typically 300% efficient) is also at least 3 times as efficient as a gas boiler (90%), again meaning a reduced demand to do the same job; see Note 2.
  3. Modal changes: By doing more to get people out of cars (as the new Decarbonising Transport report from UK Gov’t calls for) – walking, cycling and more use of public transport – we can reduce energy required for travel.  Reduced consumption and electrification are not mutually exclusive..
  4. Smoothing / lowering peak demand: On the consumption side at grid scale, there is lots that can be done to lower and smooth demand. For EVs, smart charging means we can eliminate large peaks in demand. For buildings, off-peak water heating means less wind turbines to do the same job.
  5. Energy storage / flexibility: Comes in many forms, including electrical (batteries), thermal mass (e.g. hot water tanks), pumped storage, etc. – EV cars can become part of the solution, rather than the problem, by helping to build a flexible and adaptive network at local and national scales.

These factors together mean that instead of 7 times more electricity energy per year for a future UK it would be much less than this. Even if we carry on doing more or less the same things, it would be 2.7 times more according to David Mackay (see Note 3). 

If we adopted the level of modal shift and retrofit proposed in the Centre for Alternative Technology’s ZCB scenario (Zero Carbon Britain), then we could reduce annual demand for energy by 60%, including an 80% reduction in the energy required for all forms of transport (cars, buses, planes, etc.) (see Note 4).

With Covid-19, but even before, there were many questioning why someone needs to do a 100 mile round trip for a 40 minute meeting. The digitisation of many sectors of the economy can make a big dent in the need for journeys – by any means – in the future.

And on heating our homes we can reduce our energy demand by 75%. I’ll let David Mackay do the talking (p. 153):

… can we reduce the energy we consume for heating? Yes. Can we get off fossil fuels at the same time? Yes. Not forgetting the low-hanging fruit – building-insulation and thermostat shenanigans – we should replace all our fossil-fuel heaters with electric-powered heat pumps; we can reduce the energy required to 25% of today’s levels. Of course this plan for electrification would require more electricity. But even if the extra electricity came from gas-fired power stations, that would still be a much better way to get heating than what we do today, simply setting fire to the gas. Heat pumps are future-proof, allowing us to heat buildings efficiently with electricity from any source.

Further thoughts on EVs

At this point, the Green Electrification Sceptic might say…

Ok, I see what you’re saying, but charging all the cars (that will remain at current levels for some time) is still going to need a massive increase in generating capacity, to deal with the peak load

This was essentially the argument given by an article in The Times (Graeme Paton (11th February 2017) ‘Electric cars mean UK could need 20 new nuclear plants’). 

The flaw in this argument rests on the assumptions that everyone is charging at the same time, but in reality the load can be spread, lowering the peak demand. Nationally, 73% of cars are garaged or parked on private property overnight, according to RAC Foundation. Utilities are offering deals to help them to do smart management of the grid, offering customers some perks for signing up to these win-win deals. You just tell the service provider via your charging App you want to be charged by 7.30am tomorrow morning and the software decides when to schedule you. So the peak demand will be considerably less as a result, and in fact, EVs with their batteries then become part of the solution, rather than the problem. And the charging infrastructure need not be the hurdle many assume it to be with most charging occurring at home. EVs will actually help create the flexible and adaptive grid we need in the move to renewables.

A McKinsey report on The potential impact of electric vehicles on global energy systems, concludes that the expected uptake of EVs globally is entirely manageable, assuming the relatively simple measures such as load shifting and smart charging we have discussed are deployed.

However, as a society we are still too obsessed with cars. Fetishising cars needs to end. A large EV SUV is still using a lot more resources and energy than would be needed by someone able to use regular and affordable public transport (say an EV bus), or a bike (electric or not). There is an issue of fairness at work here too, for the many people who cannot afford an EV, even a small, less resource hungry one.

Having an expensive EV car sitting mostly idle is not a great solution either, because it fails to maximise use of resources. 

In the future, people imagine autonomous vehicles which would remove the need to even own a car, and instead we would have a ‘car as a service’ via an App on your phone, which could mean we need many fewer vehicles (but maximising their usage) to cover the same miles required (the cynic might say “isn’t that a taxi?” – yeh, but minus the human driver). 

For cities, it is already questionable whether people need a car; many don’t bother because of the hassle. 

This not the case in the rural setting, so car ownership will not end anytime soon, but we need to have a major investment in public transport, cycle lanes, and cycle infrastructure in general – and policy measures like dynamic road pricing – to nudge people out of cars, as part of a comprehensive approach to decarbonising mobility and transport.

Further thoughts on Heat Pumps

Gas boilers and a lack of any charging for the damage caused by carbon dioxide emissions have encouraged a culture of flagrant wastage of energy in the UK. Someone with a house with a 6kW heat loss might typically have a 20kW gas boiler, so it can be heated in no time, even while windows are left open! 

This is our instant gratification – ‘I want it now’ – culture. 

There is no imperative to insulate the home because of artificially low gas prices (which of course will sky rocket in the future, just you wait and see).

It is the kind of attitude that ensures that when heat pumps are installed to replace gas boilers without any serious attempt to educate and monitor behaviour, the nameplate performance will be ruined by people continuing to try to heat the town as well as their homes, or oversize the heat pump and also end up killing its measured coefficient of performance (COP).

David Mackay wrote the following about heat pumps in 2009 (p.151) (see Note 5):

Let me spell this out. Heat pumps are superior in efficiency to condensing boilers, even if the heat pumps are powered by electricity from a power station burning natural gas. If you want to heat lots of buildings using natural gas, you could install condensing boilers, which are “90% efficient,” or you could send the same gas to a new gas power station making

electricity and install electricity-powered heat pumps in all the buildings; the second solution’s efficiency would be somewhere between 140% and 185%. It’s not necessary to dig big holes in the garden and install underfloor heating to get the benefits of heat pumps; the best air-source heat pumps (which require just a small external box, like an air-conditioner’s) can deliver hot water to normal radiators with a coefficient of performance above 3.

But people still seem to think it’s magic, and myths abound around heat pumps and especially Air-Source Heat Pumps (ASHPs) …

… they don’t work on older, larger homes

… they don’t perform well in cold spells

… they are really noisy

… you’ll need deep retrofit to Passivhaus levels to make it worthwhile

All untrue. But people have had bad experiences due to a combination of poor assessments, poor installation and tuning, and poor operation. 

The more insidious issue with heat pumps is that people think it’s magic that you can apparently heat a house with cold water or air. The BBC’s record on reporting heat pumps is dismal (see Note 6).

Now, because only a minority or householders have a water or ground source sufficient to heat their homes, so the assumptions is that we would expect the great majority of homes to use air-source heat pumps (ASHPs).

The ‘Green Electrification Sceptic’ will say they understand how heat pumps work, but then repeat some of the myths around ASHPs and say that the Seasonal Coefficient Of Performance (SCOP) – the COP averaged over the year – is not the oft quoted 2.5 for ASHPs, but 2 or even lower. What I think this reflects is bad experiences based on poorly installed or operated systems. This bad experience – in some cases dating back years – is being used as a reason to reject ASHPs.

I attended an excellent webinar hosted by Carbon Coop from Paul Kenny, former CEO of the Tipperary Energy Agency who conducted a pilot, including many homes (working with the Limerick Institute of Technology to assess the results).  The video recording is here  and his slides are here. These were all ASHP installations.

During a period of October 2017 and May 2018 the overall COP ranged from about 2.6 to 3.6 and averaged 3.1, pre-optimisation. During an exceptionally cold 2 week period, where external temperatures were down to minus 6oC, the COP was never below 2.5 and ranged from 2.5 to 3.

Key points to note:

  • They did necessary and sufficient retrofit but not to a Passivhaus standard.
  • There was no external wall insulation, for example.
  • They did not upgrade 2 panel radiators to 3 panels. They did pragmatic emitter upgrades.
  • When asked whether it was worth going for a Ground-Source Heat Pump (GSHP) because of extra nameplate SCOP, Paul Kenny said no, because if one has some extra money, they should spend them on upgrading emitters (e.g. get those 3 panel radiators), and you can close the performance gap without the disruption of digging up an area of garden (assuming one has that option, which many won’t have).

It is a very positive story of how to make ASHPs successful (and, btw, Carbon Coop are a great source of material, sharing real-world experiences of whole house retrofit).

He does caution that one needs a properly qualified assessment done, and ‘sufficient’ remedial retrofit is obviously required. But properly sized and installed, there are really no issues using the approach they have now refined. Every house is different, but the ingredients are the same.

He cautions also against oversizing a heat pump (and I think the combination of EPC (Energy Performance Certificate) and RHI (Renewable Heat Incentive) may push this outcome sometimes, by being pessimistic about the achievable SCOP), because then they may well be kicking in and out of operation, and this will kill their measured COP.

Increasingly we are seeing ASHP and PV combos (see some examples from Yorkshire Energy Systems here) because, while the peak need for heat and minimum for solar PV coincide in the year – hardly ideal – the ‘shoulder seasons’ (Spring and Autumn) do provide significant benefits, and some households are finding the net cost of operation competitive with gas. When, finally, gas attracts the level of carbon tax it deserves, it will make it easy for ASHPs to compete on a level playing field in price terms.

Final Thoughts

I support the call for reduced consumption in all its forms, and it should be encouraged as much as possible, but this is not mutually exclusive with electrifying transport and heat. On the contrary, electrification helps in this endeavour, because of increased efficiency and flexibility. But it needs to be coupled with approaches that ensure  fair access and market reforms.

We need to acknowledge the issues hitherto in increasing the skills base for retrofit and renewable heat, and improving the quality of installs, but that is not a good argument for dismissing heat pumps. It’s an argument for a major push on the required training and quality systems, something the Government has lamentably failed to prioritise.

As CAT ZCB says, we need to ‘power down’ (stop wasting energy, use it more efficiently, and change some behaviours and norms), but then ‘power up’. The power up bit requires a lot electricity from renewable capacity, and a fair amount of storage too. They have a plan we can get behind.

Currently, the UK Government does not have a coherent plan across all sectors, but whatever plan we decide to finally put some real effort into, it needs to be one that stacks up.

And for those that claim that the CAT ZCB models and assumptions are optimistic, it is worth looking at others who are independently modelling the transition, and are optimistic about our ability to decarbonise the grid in relatively short timescales (see this commentary on a Colorado study).

As the sadly departed David Mackay said, he was not biased in favour of any one solution, but was in favour of maths. We all need to be fans of maths, and be clear about our assumptions, when conceiving and debating options.

Ultimately, electricity is a great democratiser of energy.  Generation is de-coupled from consumption in a way that was not (and never can be) true for fossil fuels used for cars or heating homes.

If you consume electricity in a light bulb, EV car, heat pump, fridge or lawn mower, you can take the renewable energy from any source – a wind turbine array in the North Sea, or a community energy scheme, or the solar PV on your house. All powered ultimately by the sun.

It is not surprising that those who have controlled the energy supply chains – from exploration and production to the petrol station forecourt or gas metre at your home – are putting up a fight to retain control, including greenwashing galore, and fake green gases, with the help of lobby groups and big marketing budgets, which is nothing to do with finding the right solution for consumers or the planet (as the dash for methane gets marketed as a dash for Hydrogen).

What is more surprising is that greens do not always appreciate the importance of electrification to both the decarbonisation and democratisation of energy.

It’s time they did.

(c ) Richard W. Erskine, 22nd July 2020


NOTE 1 – EV efficiency compared to Internal Combustion Engine (ICE)

EVs are about 90% efficient (so for every 1kWh of energy in its battery,  an EV will use 0.9 kWh to do work), whereas the Internal Combustion Engine (ICE) is typically around 30% efficient (so for every 1kWh of potential energy in the fuel, only 0.3kWh will do any work). That is a relative efficiency of 3 to 1 (in both cases excluding the energy losses between the engine and moving wheel).

Another way to calculate it is to take a figure of 60 mpg figure for a petrol car, and using a figure of about 30 kWh per gallon, that equates to approximately 2 miles per kWh of primary energy for a petrol car. Whereas, this source indicated 41 kWh battery capacity for a Cleo with a range of 250 miles, this is (250/40) approximately 6 miles per kWh. So, again, a relative efficiency of 3 to 1 in switching to a similar sized EV car.

NOTE 2 – Unravelling hydrogen hype 

David Mackay said in Sustainable Energy – without the hot air p. 129: 

Hydrogen is not a miraculous source of energy; it’s just an energy carrier, like a rechargeable battery. And it is a rather inefficient energy carrier, with a whole bunch of practical defects.


A hydrogen cell car is about 40% efficient in its end-use of energy, whereas an EV is 90% efficient. If it is ‘green hydrogen’ created from a wind turbine through electrolysis, the overall efficiency for the hydrogen cell car is roughly 50% * 40% = 20%. Whereas for the EV it is 90% efficient (in both cases ignoring relatively minor network losses – for gas or electricity – and in both cases excluding the energy losses between the engine and moving wheel).

20% versus 90% is not a great look for hydrogen cell cars, and would mean (9/2 =) 4.5 times as many wind turbines to support the same level of green mileage by UK drivers.


And if hydrogen is a poor choice for cars, then providing ‘low temperature’ heat for homes is a little crazy in my view. Whatever hydrogen we do produce needs to be reserved for high temperature industrial applications.

In Getting off gas: future risks for energy poor households (15th July 2020) Louise Sunderland wrote

But fossil gas is not the fuel of 2050. Hydrogen appears to be waiting in the wings to replace fossil gas in the grid. However, hydrogen is unlikely to be available in large quantities across Europe for home heating, as the available hydrogen goes first to those uses that rely on high temperature heat – which hydrogen can produce but electricity cannot. In the various 2030 and 2050 European decarbonisation scenarios, hydrogen for use in buildings is almost absent in 2030 and provides a small share of energy consumption in only some 2050 scenarios.

Importantly, projections show hydrogen will likely be significantly more expensive than a heat pump for home heating, and adapting to hydrogen will require upgrades of both the grid and home heating systems.

The availability and cost of hydrogen for domestic heat are at best uncertain. If low-income households are disproportionately reliant on gas, they will pay higher costs for infrastructure and be open to the uncertainty and price shocks of replacement fuels. 

Sourcing Hydrogen

An important question is: where would the energy come from to manufacture the hydrogen? Fossil fuel companies would love that we continue to source it from methane (currently 95% of hydrogen is produced this way), but a by-product is carbon dioxide, and then you have to believe it can be successfully buried using ‘carbon capture and storage’ (CCS). Yet CCS is unproven at the scale needed, and the timescales require urgent action. So the full supply chain for hydrogen today is far from green. And then there is the cost of storing this gas, and the infrastructure.

A study done for the Climate Change Committee in Analysis on abating direct emissions from ‘hard-to-decarbonise’ homes (Element Energy & UCL) , July 2020 looked at different scenarios. Interestingly it seems that for those scnearios involving hydrogen, the (probably prohibitive) costs of CCS and the storage off hydrogen are not included in their comparative cost analysis (because of their uncertainties). Whereas the oft stated hurdles for using widespread adoption of heat pumps such as developing the supply chain and raising the skills (relatively trivial things to fix) are highlighted ad nauseum.

But these hurdles could be addressed tomorrow, with an appropriate push from Government (e.g. legislating for air-source heat pumps for all new builds and post-build energy performance certification; and no gas connection). This would force the laggardly big boys in construction to institute the training required and pump-prime the supply chain. It ain’t rocket science. The UK Treasury need to end the short-sightedness that killed the zero carbon homes plan and the Government should tell the UK’s largest house builder to pull their fingers out!

Other ways of producing hydrogen exist, one of the most talked about is by electrolysis using excess energy from renewables, producing so called ‘green hydrogen’, but that these will never be greater than 100% (and electrolysis is around 50% efficient), so can never compensate for the lower of efficiency of hydrogen-cell cars when compared with EVs. 

And as Tom Baxter says in The Conversation, Hydrogen isn’t the key to Britain’s green recovery – here’s why

Much of my 45-year career in industry and academia has been spent studying energy efficiency and power production and supply. I believe that hydrogen has a limited role in decarbonisation, and that businesses with a vested interest in promoting hydrogen are doing so at the expense of British consumers.

Michael Liebreich has written on the economics of hydrogen in Separating Hype from Hydrogen, both on the Supply Side and Demand Side.

He has also published a Hydrogen ‘Use Case Ladder’ showing which applications of hydrogen make sense and which don’t. Cars and Heating are in the ‘don’t make sense’ section of the ladder (see NOTE 7).

Now, new research on the full life-cycle of ‘Blue Hydrogen’ shows it is anything but low carbon.

Hydrogen will play an important role in industry, and on the electricity power grid, providing a form of stored energy that addresses need to balance generation and demand over longer periods. Michael Liebrich shared a figure – the hydrogen use ladder – showing where hydrogen can/ should be used, and where it shouldn’t:


Whichever way you look at it, the hype around hydrogen around transport and heat is overblown.

Synth Gas

Nevertheless, there will need to be a role for synthetic gas – hydrogen or others – as an energy carrier and/or storage medium. 

The CAT ZCB report includes a significant role for synth methane for energy storage and backup. Their argument being that they can leverage existing gas infrastructure for backup power generation, for example, using truly green synth gas (so no CCS required).

Chemical storage is an important potential complement to gravitational (pumped storage, hydraulic storage) and battery storage, because it can be inter-seasonal in scope. But each must be judged according to its qualities (cost, carbon intensity, capacity, latency, storage, transmission, etc.).

Imagine arrays of solar PV in the Sahara generating electricity; how do you get that energy to where it is needed (Africa and Europe, say)? It could be via an electricity distribution network, but could also be by producing synthetic gas, and transporting that gas via pipelines. If the gas is easy to liquify (as Ammonia is), other options are possible. Instead of Liquified Natural Gas (LNG) from Qatar, we could have liquified renewable sunshine from Australia, which could become a leading post-coal energy exporter, with the help of Ammonia.


Ultimately, though, electricity is a great democratiser of energy, when freed from fossil fuels in its generation. Heat Pumps can get their electricity from any low carbon source and so, as David Mackay said, are future proofed.

NOTE 3 – Sustainable Energy without the hot air (2009), David Mackay

This book, available online, should be required reading for anyone who wants to discuss how to decarbonise a country’s energy supply and usage, not because it was the final answer on any scenario (nor claimed to be), but for its approach, which was to provide a tool kit for thinking about energy; to increase our energy literacy. The kiloWatthour (kWh) is a usefully sized unit of energy employed throughout the book, and also one that appears on our utility bills. A kWh per person per day (kWh/p/d) is a measure that makes it simple to assess our average consumption, and compare different options.

Mackay showed how energy consumption in UK would drop purely through electrification (assuming we still do more or less the same things), and since fossil fuels would be displaced by electricity generated without fossil fuels, we would eliminate most of the carbon emissions, but of course, the electricity generation would need to increase in the process (Mackay said that 18kWh/p/d should rise to 48kWh/p/d, or an increase by a factor of about 2.7, or an additional 170% electricity capacity) – See Figure 27.1 on p.204:

Mackay electrification

NOTE 4 – Centre for Alternative Technology’s scenario

 In Zero Carbon Britain: Rising to the challenge (2019), by the Centre for Alternative Technology (CAT) a breakdown is provided of the 2017 energy supply and consumption for UK as follows: 

ZCB UK energy 2017

Inefficiencies exist in the combustion of fossil fuels to produce useful ‘work’, but also in different end-use settings, such as electrical white goods (e.g. fridges) and lighting.

There are also reductions in demand possible by changing some of the things we do today, such as increasing the use of walking, cycling and public transport compared to car use, for example. Taking all those into account, CAT propose a 60% reduction in demand in their ZCB scenario: 

ZCB 60% reduction

How is demand reduced? For homes, it is a combination of retrofit and smart controls: 

ZCB home heat performance

For transport it is mainly through reductions in car use and electrification of transport 

ZCB transport 1

Leading to a very large reduction in transport energy demand …

ZCB transport 2

 NOTE 5 – Net efficiency illustration

In this quote from Mackay, he mentions a net efficiency of using gas to electrify heating, based on a Figure provided on page 150. I will do a simple calculation to illustrate a net performance figure. Mackay used a figure of 53% efficiency for gas powered electricity generator (top of line at the time of Mackay’s book) and an 8% transmission loss (92% transmissions efficiency); and an ASHP between COP of 3 – at the lower end of modern ASHPs – and 4.  The overall efficiency would be in the range between 0.53 * 0.92 * 3.0 = 1.46 and 0.53 * 0.92 * 4.0 = 1.95, that is, between 146% and 195% efficiency.  Mackay uses the range 140% to 185% in the quotation. The point being that any of these figures is much greater than the 90% efficiency from sending the gas to a boiler in the home to provide heating.

NOTE 6 – Heat Pumps are an old idea and not magic

By the mid 19th Century heat was understood as the jostling of atoms – the ‘kinetic theory of heat’ as pioneered by Maxwell and Boltzmann. The greater the temperature above absolute zero (0 Kelvin or -273.15 Centigrade) the greater the average velocity of molecules. A sea of water at 5oC contains a huge amount of thermal energy. We should be careful not to confuse the temperature of a body with its energy content! The energy content will be a function of the temperature and volume of the body of water (the same principle applies to a body of air). With a large enough volume, the temperature becomes relatively less important; there will still be plenty of energy to harvest.

The genesis of the heat pump dates back to the early-mid 19th Century, but the first water-sourced one was installed in Switzerland in 1912. Heat pumps are neither new nor extraordinary.

There is no magic. Heat pumps harvest the ambient heat (which can be in the air, ground or water) that ultimately derives its energy from the Sun. This is done through a process that is like a reverse fridge, but in this case moving heat from the outside (often at a relatively low temperature) to the inside (at a relatively higher temperature), with the help of a refrigerant medium and a pump and compressor. No magic is required, just a little A-level physics. 

Typically, if a heat pump uses one unit of electrical energy to drive the system it produces three units of heat. This equates to a 3/1 = 3 efficiency factor, or 300%. 

Roger Harrabin, is the BBC’s Energy and Environment Analyst. This is what he said in a report on a water-source heat pump installed to heat the historic house of Plas Newydd in Wales (science facepalm warning):

It’s barely believable that this sea water has enough heat to warm anything, it’s pretty chilly at this time of year, but yet, thanks to an extraordinary technology called a heat exchanger, it’s the sea that’s going to heat this house.

It is incredible but true that a BBC energy correspondent appears to not understand the distinction between the temperature of a body of water and its thermal energy content, and believes the technology is novel and new. This is not the only report he has made on heat pumps that demonstrates a complete misunderstanding of how they work. 

The gas network lobbyists championing allegedly sustainable gas in various forms must absolutely love Roger.

NOTE 7 – The Use Case Ladder for Hydrogen

… o o O o o …


Filed under Renewables, Transition to Low Carbon

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 installation. No, you can only have 4kW per phase before seeking permission from the grid (kW here mean kWp, the peak kW power achievable).

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 panels has dropped while their performance has increased (output increased from 250W to 350W 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 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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Filed under Renewables