Can biomass help meet the UK’s energy demands?

Reposted from Science Omega online
As the world’s supply of fossil fuels dwindles, the search for alternative energy sources is vital. Biomass is one such energy source that is being touted as a good alternative to conventional fossil fuels. However, it is not without considerable opposition from those who argue that biomass could do more harm than good in the battle to reduce greenhouse gas emissions.

Biomass is energy created from the burning of biological materials such as plants and non-living things such as biodegradable waste. Anything that is alive or was alive a short time ago can be categorised under biomass, therefore trees, crops, animal and plant waste are all included.

The attraction of biomass in the fight against climate change is that it is carbon neutral. Unlike the fossil fuels, oil, gas and coal, which when burnt add to the net amount of carbon dioxide in the atmosphere, the CO2 that biomass produces when ignited is absorbed from the atmosphere by the crops used to make it, and so the net atmospheric amount is not increased.

“It is clear that for biomass to be part of a zero-carbon energy future, strict safeguards need to be in place to ensure that only sustainable sourcing occurs. “

Currently in the UK there are 20 dedicated biomass power plants that are producing a total of 1,092MW from a variety of sources including poultry waste and woody biomass. There are around another 30 at planning stage with a combined capacity of 5,000MW.

Given that 1MW can sustain 1,000 homes for an hour, that is a significant contribution to the UK energy mix. However like many energy sources, it is also controversial, as there are both advantages and disadvantages.

In recent years numerous organisations have issued warnings about the potential impacts of the mass production of biomass. UK-based organisation Biofuelwatch is currently protesting against plans by Drax power station in Yorkshire to convert half of their coal-fired power station to run on biomass. Whilst in practice this sounds like a green idea, “highly biodiverse forests in North America are already being clear cut to make wood pellets for UK power stations. This will only get worse as the industry expands.”
Biofuelwatch say that communities in South Africa are already losing access to land and water because biodiverse grasslands are being destroyed for monoculture tree plantations, some of which supply Drax.

Drax has the capability to produce 12.5 per cent of its output from renewable and sustainable biomass – the equivalent output of over 700 wind turbines. Drax says that ‘burning biomass at this level saves over two and a half million tonnes of CO2 each year.’

Wood has always served as a fuel source for fires and ovens, however technological advances mean that burning biomass can produce energy for everything from a power plant to an engine.

The advantages are that burning biomass is said to be carbon neutral, in that by growing and then burning it there is no creation of additional carbon monoxide. Biomass products are abundant and renewable; since they come from living sources and life is cyclical, these products potentially never run out, so long as there is something living on earth and someone is there to turn that living thing’s components and waste products into energy.

Another benefit of biomass is that we can use waste and thus reduce landfill to produce energy. However there are concerns that incinerating household waste depresses recycling and wastes resources, releases greenhouse gasses, and is often forced through against strong public opposition. Instead of promoting zero waste, incinerators rely on material for feedstock that should be recycled or composted. Incinerators create toxic emissions and hazardous ash, and therefore pose significant health risks.

It is clear that for biomass to be part of a zero-carbon energy future, strict safeguards need to be in place to ensure that only sustainable sourcing occurs. Otherwise, as the Centre for Alternative Technology’s Freya Stanley-Price points out: “We are getting rid of one environmental problem and replacing it with another.”

Friends of the Earth suggest a number of measures that include keeping the scale of biomass to the size of domestically available resources, using anaerobic digestion for the treatment of food and animal waste and focusing biomass use close to production.

In addition, there must be a joined-up, integrated approach to energy planning that considers the most efficient use of any energy generated and looks forward to managing energy demand.

“There are many things that have to be carefully considered and weighed when determining if biomass energy is a viable alternative energy source,” Stanley-Price says. “In a zero-carbon future we must make sustainable use of trees as fuel, and replant them as we harvest them – creating a continuous carbon cycle. Growing our own fuel also creates jobs and is ideal for strong, local economies.”

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What really happened on Any Questions held at ‘eco loon central’ on Friday Night?

Following ‘the rowdiest’ Any Questions in programme history held at the Centre for Alternative Technology in Machynlleth – complete with anti badger culling and anti wind turbine protests – James Delingpole wrote a blog, published in the online Daily Telegraph, attempting to clarify his side of the story.

As someone who works at CAT, my take on the evening was unsurprisingly a little different: the real shock of the programme was not the anti wind farm cheering or right wing loon James Delingpole! It was something a whole lot more sinister. Secretary of State for the Environment Owen Paterson was asked if he agreed with James Delingpole’s opinion that climate change was anti-scientific, ideological nonsense. His response might come as something of a surprise given this man’s role in the UK government. Apparently the climate and temperature have not changed in the last 17 years. Jaws dropped in disbelief, and Peter Hain managed to splutter a reply: “and this i s the minister for the environment.”

It was always going to be a lively programme: from the moment word got out that Any Questions was happening in Machynlleth both pro wind farm and anti wind farm groups started ringing up for tickets. The news that Owen Paterson was going to be on the panel excited everyone, and when James Delingpole was announced it seemed like a BBC set up. Bring two wind turbine hating public figures to Europe’s leading eco centre, pitch them against socialist, republican, Welsh nationalist Leanne Wood, and well, let’s see what happens.

Earlier on in the afternoon a small but vocal group of people dressed as badgers had started a demonstration in the car park. A brief blockade of ‘badger killing’ Owen Paterson’s car followed, but all in all it was a good-natured affair. Those ‘desperately earnest and well meaning’ volunteers, so well described by James Delingpole in his blog, did their jobs of showing people to their seats and generally being welcoming and polite.

As the evening began, the atmosphere was electric. Encouragement from BBC warm up man Peter Griffiths and then Jonathan Dimbleby for audience participation was perhaps not necessary, given how the evening unfolded. The audience were opinionated, lively and more than willing to respond to answers from Leanne Wood, Peter Hain, Owen Paterson and James Delingpole.

There were a lot of interesting moments, much cheering, some booing. It was a pleasure to host the event at the Centre for Alternative Technology, not that we imagine that BBC Any Questions will be coming back in the next 40 years!

But those few words, buried amongst the cheering, booing and angry badger man’s outburst, stand out in my mind as the most disturbing revelation by BBC Any Questions on Friday night. Cabinet Minister for the Environment – not Welfare, Education or Defence – clearly stated “The real question is: is climate change influenced by man made climate change? The climate, the temperature has not changed in the last 17 years.”

Unbelievably, the UK has a Secretary of State for the Environment who believes that climate change is not happening; you couldn’t make this stuff up. It‘s absurd that as the level of carbon emissions in the atmosphere reaches 400ppm, as people around the world struggle in the face of adverse climatic conditions, as India bakes and Central Europe floods, as think tanks and NGOs advise that climate change will cause food shortages, political instability and rising sea levels, the Secretary of State for the Environment for the UK can sit glibly in front of an audience, on national radio, and say that climate change is not happening.

What’s more, when asked if local protests against wind farms should be able to stop developments from going ahead, he responded with a clear message that from now on landscape, topography and heritage should take precedent over national energy targets. Leanne Wood’s valuable point that this should be rolled out to include all energy generation stations was a little lost on him. For him it’s the wind turbines that are the problem.

It was shocking what happened on Friday night at BBC Any Questions. Any illusions of “greenest-ever” governments or intentions to tackle climate change and reduce carbon emissions in the UK were shattered into pieces.

I thought that James Delingpole was going to be the right wing loon on the Any Questions programme on Friday night, but I was mistaken: it was Owen Paterson. The problem is that his ramblings are not confined to the back pages of the Daily Telegraph – he is a cabinet minister and he is responsible for the environment.


This week at CAT; Radio 4 programme Any Questions

The Centre for Alternative Technology is delighted to welcome the Radio 4 program, Any Questions to its sustainable education centre WISE on the 7th of June 2013.  Any Questions, hosted by Jonathan Dimbleby was first broadcast in 1948. Every week it visits a different part of the country with a panel of 4 speakers who answer questions from the audience. The programme provides the opportunity for people to challenge politicians, policy makers, writers and thinkers.

The current panel for the evening is Ann Clwyd, Owen Paterson and Leane Wood. Ann Clwyd Roberts is a Welsh Labour Party politician who has been the Member of Parliament for Cynon Valley since 1998. Owen William Paterson is a British Conservative Party politician who has been the Secretary of State for Environment, Food and Rural Affairs since 2012 and the Member of Parliament for North Shropshire since 1997. Leanne Wood AM, is a Welsh politician and the leader of Plaid Cymru

The quality of the questions that the audience ask is crucial to the success of the programme. The producers look for questions on the most stimulating, moral, political and social issues of the day- the issues that get people talking.  At CAT the Any Questions box will be at the reception when the public enter from 18:00 and the audience can fill in their questions then.

For more information and for free tickets please contact 01654705957




Catching up with our water and natural resources volunteers

A report from our wonderful water and natural resources volunteers on the work they have been doing.

Managing the woodland:
Coed Gwern is 15 acre woodland managed in a sustainable way by CAT, ensuring and enhancing biodiversity. The spring season is a very important time because many of the migrant birds are coming back to our woodland and life increases after the long stopped of the winter season –bird nesting, trees blossom, etc-.

Throughout the spring we have been making bird boxes and cleaning coppice areas, a special work related with two different protected species: Willow tits and Dormice. A number of areas of the woodland have been prone to flooding and we have been managing this by building dams and ponds, to retain the rainfall. This should help the different bird species (migrants and residents) to nest and find food supply for their chicks and themselves.

The CAT woodland is a great home for willow tits

However, we don’t just build ponds and dams to slow water down or retain it. Recently we built a small pond in front of the bird hide at Coed Gwern so birds can drink out of it and even maybe bath.

Needless to say that these watery places will just be heaven for species who like getting wet. Pond skaters (these large mosquitoes look alike insects skating over the surface of the water) are usually the first ones to appear, then will come other invertebrates like dragonflies, spiders and frogs.

Monitoring changes: In January 2013 the Water and Natural resource department started an exciting new project involving the local community. The woodland is divided in 24 monitoring points which have been adopted by different people and groups. Through this project we are able to follow changes in the plant and animal life.
We have also been improving the network of paths and walks, placing signs to facilitate a good use of the woodland by visitors.To get involved in the woodland monitoring project contact:

Spring’s also the time to find out bird nesting sites. So  two monitoring routes were chosen and measured (100 meters long each) to survey bird species on a map once a week. This work, carried out over 5 weeks requires bird call and song listening skills as well as identifying birds. This work will enable us to draw up a map of the different nesting sites across Coed Gwern

Art in the woodlands: We have been involved in a biodiversity and arts project, developed by Jony Easterby, to build an artificial pond in the woodland. The pond is designed to be both a natural space for people to enjoy and promote water conservation.

Greenwood crafts: As one of the main activities in the winter and spring months is clearing, it makes perfect sense to use the cleared wood for building gates, fences and splitting logs for firewood next year.

The bird hide builders

Building Bird hides: In the last two months CAT volunteers have been working in a project to build a bird hide in the slate quarries, old dynamite hut. Wall stones were removed shifted, added, levelled and rubble was taken out of the ground to even it out. Once the walls were at the right height, the wood work came along (timber frame for the roof and planks above the walls and under the roof with openings to make it a proper bird hide). Last but not least it has got a proper metal roof, which provides good shelter for bird-watching and listening, rain and sun. So the bird hide is now up and roofed. We are now working on displays to help visitors identify woodland and field bird species, and benches to just sit and enjoy the different sounds of nature!

Worm research: We have continued with research that started last year into the use of tiger worms and compost toilets for developing countries

For more information on volunteering and working at CAT please check our webiste, we currently have a number of positions open for volunteers.

Solar Ovens in Wales

The Centre for Alternative Technology was delighted to receive a solar oven (also know was a parabolic cooker) as a gift from a recent visitor to the centre. Manolo Vilchez, from the social enterprise Alsol, based in Spain, fulfilled a long term goal to visit the Centre this week. He presented CAT with a solar oven produced by the organisation he works with as a gift for use as part of our educational work.

The solar oven

Paul Allen, External Relations Officer at CAT said: “It is a wonderful gift to receive and we have already seen how on this cloudy day the sun is heating the pan, even in Wales.” Alsol works across Europe in providing solar products, with a strong emphasis on co-operation and educational development.

A solar oven cooks by turning light rays from the sun into heat; the sun is the fuel source. Reflectors on the solar oven direct the light towards a dark pot, which helps to absorb the heat.

Inspired by a previous model, CAT’s new oven has been designed and manufactured entirely in Spain.  The parabolic cooker can be used to fry, bake, roast and even cook bread. The ALSOL 1.2 is a powerful machine that uses clean, renewable energy from the sun to produce up to 7 litres of  boiling water daily.

Since solar ovens do not require any fuel other than the sun, they are becoming very popular in developing nations in Asia, Africa and Europe. They are relatively inexpensive so many charitable organisations have begun to distribute them to people in areas without other options for power. Solar ovens can provide an environmentally responsible cooking solution for people all over the world.

Manolo explaining how the solar oven works
Manolo presenting the solar oven to the CAT team

Communicating the Communications Officer Role

The research period for the latest Zero Carbon Britain report is coming to a close, and we are now looking ahead to the communications phase of the project. We are recruiting for a Communications Officer to work alongside the current ZCB team, co-ordinating the communication of the new research findings, aiming to build awareness, stimulate debate and discussion, and catalyse further action amongst our target audiences.

Paul Allen, CAT’s Director of External Relations, talks about the roles and responsibilities of the post…

“We’re coming to the stage where we’ve completed the most recent year’s research. Because the 2010 report had such an impact in that lots of people were using it, lots of people were talking about it, the dialogue that came out of that made us recognise that there were some things where we couldn’t answer people’s questions. Not because what we’d got was wrong but because we hadn’t got enough detail. Particularly things like land use, diet and dealing with variability and balancing supply and demand. We recognised we needed to do some more work.

So we’ve been researching and burying our heads in data and looking at outputs from actual offshore wind farms, not theoretical models. Correlating them against actual Met data and scaling it up to give us an indication of what the profile of energy generation would be, and then comparing that with the demand profile and coming up with a new report which will be much much more detailed.

Paul Allen and Peter Harper discuss the 2010 ZeroCarbonBritain report

The new person’s job will be to run a communications strategy based around that research. We’ve got a draft aims and objectives of the communications plan and their first job is to go through that and add more detail to research into the different markets, look at the mapping that we’ve done, look at where the different target groups are now and what tools and resources we might need to develop. But primarily I think it’s looking at communicating it through CAT, because CAT’s clients are the people who are interested in this in any case and we’re surrounded by the sort of infrastructure that helps bring the point across.

It’s also about getting it out to other groups who can act as amplifiers of the message, particularly through developing the ‘ZeroCarbonBritain and…’ two-pagers, which seem to have worked very well in getting other people to think: ‘well what would it mean for refugees’ or ‘what would it mean for Egypt’ or all sorts of other things. So they will be building on that, developing more of those and so bringing in more groups. Also working with arts, creative practice and we’ve put some money in a budget to have ZeroCarbonBritain activities happening on the site, and it won’t be just kids activities, it’ll be family activities for the adults as well as the kids. And the new Comms role will be managing that, working out how we can take Laura’s Larder or Tobi’s energy game and do it this summer, for real, with the visitors…

It’s a chance to find somebody who is technically fluent, who’s got a science or an engineering background, who isn’t going to be completely flustered by somebody asking questions. I think it’ll be a really interesting job for whoever gets it. It’s the chance to work on cutting edge, state of the art thinking about how we grapple with 21st Century challenges. It means not having to beat on about the negative side of Climate Change and the worrying side for frightened looking polar bears on diminishing icebergs but to spout on about exciting visions of positive futures where we can cross the changes that we need to make to decarbonise with changes that can increase well-being, or more habitat, or economic recovery, or the jobs part of it. So there’s lots of positives there.”

Application packs can be downloaded from the CAT website.

More information about ZeroCarbonBritain can be found here.


Glue Laminating at Grand Designs Live

This year CAT has been on bit of a promotional tour – travelling to London, Birmingham and London again to attend exhibitions, study fairs and conferences. Each event gave us the opportunity to talk to people about CAT’s work in the field of sustainability. From this coming Saturday however, CAT will be doing more than just talking.

We’re spending nine days camped out in the miniature village that is Grand Designs Live at the ExCel in London. Each day CAT will be providing demonstrations of glue laminating (or glulam) used to build the beautiful ‘wigloo’ you can see onsite in Wales. Jules, the carpenter who designed the toilet in association with Crafted Space, will be doing two demonstrations each day. As well as this, we have some examples of sustainable building techniques with us and the opportunity for people to ask CAT experts questions about their building woes.

Timber Arc Compost Toilet
The glue laminated compost toilet up at CAT

So what exactly is glue laminating?

It’s a process where several layers of timber are bonded together using a durable, moisture-resistant adhesive. The resulting structure can be used in both straight and curved configurations. The build that Jules undertaking requires curved lathes so he uses a ‘former’ to help hold the layers in place as the glue dries.


So why glue laminating?

Glue laminating has much lower embodied energy than reinforced concrete and steel, although of course it does entail more embodied energy than solid timber. However, the laminating process allows timber to be used for much longer spans, heavier loads, and complex shapes.

Glulam is two-thirds the weight of steel and one sixth the weight of concrete – the embodied energy to produce it is six times less than the same suitable strength of steel. Wood has a greater tensile strength relative to steel – two times on a strength-to-weight basis – and has a greater compressive resistance strength than concrete. The high strength and stiffness of laminated timbers enable glulam beams and arches to span large distances without intermediate columns, allowing more design flexibility than with traditional timber construction.

Glue Laminating
Jules clamping some glue laminated timber onto the former

We’ll be following the build live each day over on Facebook so have a look and see how it progresses!

If you like the look of the compost toilet, take a look at Jules’ website.

Grand Designs Live is open to the public from Saturday 4th to Sunday 12th May. More information can be found on their website.


CAT pioneers reunite for BBC Radio 4 broadcast as 40th anniversary approaches


Five early pioneers of the Centre for Alternative Technology were reunited on Sunday 28th April for BBC Radio 4’s The Reunion. Hosted by Sue MacGregor, The Reunion takes a weekly look at significant events and moments in history by reuniting the people who made them happen. Past programmes include the first years of Doctor Who, the 1948 Olympics, and the founders of Comic Relief.

On April 28th it was the Centre for Alternative Technology’s turn, as Sue brings together CAT’s first Technical Director Bob Todd, and his wife Liz, CAT’s first and second Directors Mark Mathews and Rod James, and Pembrokeshire builder Des Rees, who wanted to have an adventure in the Sahara, and found himself working in a damp slate quarry in mid-Wales instead! There will also be recordings of now-deceased founder Gerard Morgan-Grenville, leading environmentalist Jonathon Porritt and long-term staff member Peter Harper, who first coined the term ‘alternative technology’.

In November 1973 CAT founder Gerard Morgan-Grenville signed a lease on a disused quarry owned by Old-Etonian school friend John Beaumont. On it he planned to build ‘The Village of the Future’. The National Centre for Alternative Technology was to be powered by renewable energy, fed with organic produce and run under co-operative principles.

The Centre defied conventional approaches to energy and food production, developed innovative technologies and spawned hundreds of like-minded projects and enterprises across the globe. The first ‘pioneers’ moved on-site in 1974, and CAT will be celebrating its 40th anniversary in 2014.

The Reunion will also use interviews collected via CAT’s Oral History Project, which was funded by GLASU and organised by Allan Shepherd.

“With CAT’s 40th anniversary coming up in 2014 we’ve been preparing an archive of written, oral and photographic stories about the Centre’s history, some of which will now feature in The Reunion,” explains Allan.

“The whole archive will be kept in the National Library of Wales in Aberystwyth and will be launched as part of a series of events and activities we have planned for CAT’s 40th anniversary in 2014. The Centre has played a part in the lives of hundreds of thousands of people, as well as making a big impact on environmental thinking. The Reunion recognises this, and the programme is a fitting tribute to CAT’s history.”

The Reunion is broadcast on BBC Radio 4 on Sunday 28th April at 11.15 and May 3rd at 9am, and is also available online.

Contact for more information about the CAT Oral History Project, archive or 40th anniversary celebrations; and for CAT media enquiries.

BBC Radio 4 will also be bringing Any Questions to CAT on June 7th. Any Questions is a question and answer broadcast featuring a live studio audience and a panel of politicians from all major parties. It will be broadcast from the WISE building at CAT, and CAT will be looking for a live audience closer to the time. Contact for more information.


The top 5 renewable energy questions from the National Homebuilding and Renovating Show

If you went to the National Homebuilding and Renovating Show a week ago, you might have been inspired by the live demonstrations of thatching, or felt the sudden urge to redecorate when you passed the stall full of sheepskin rugs. Or perhaps you realised you really did need a 2-metre 3D TV in your lounge, or maybe you simply wanted to browse whilst enjoying an ice cream from the Yorkshire Dales food cart (it’s a permanent installation).

Nestled between two full-size timber frame houses, one of which was the Eco Home Theatre, the CAT stall was a small hub of renewable energy debate in this varied crowd. Enthused by Tobi’s daily talks, a stream of visitors made their way to us to ask often highly specific or technical questions. Some of the same concerns kept coming up, so we’ve collated a list of the five most common questions and Tobi’s answers.

Lots of people also asked us questions about architecture and design, but we’re going to save those for a later feature. Stay tuned!

  1. What’s PVT, and is it a good idea?
  2. Is there a case for thermodynamic systems?
  3. Are heat pumps right for me?
  4. Micro hydro: yes or no?
  5. Should I heat my house with biomass?


1. What’s PVT, and is it a good idea?

PVT is the combination of solar photovoltaic systems (the “PV”), which produce electricity, and solar thermal systems (the “T”, also known as solar water heating, SWH), which produce hot water.

In principle, you can see the potential for synergy between these technologies. PV modules convert only 10%-20% of the solar energy that falls onto them into electricity, and a good proportion of the remaining solar energy is converted into heat – solar PV get hot in the sun. So why not use this heat to heat water for showers? This is what PVT modules do – basically, they are solar PV modules put onto a solar thermal absorber. In principle, this is a brilliant idea. In practice, it’s not so easy.

Solar PV modules actually operate more efficiently when they are colder (because their electric resistance is lower) whereas for your showers you want your water to be hot. Under some conditions that works out perfectly – as long as your hot water cylinder is cold, the solar thermal part will actually cool your solar PV module down. But on a sunny summer’s day you ultimately want your solar thermal system to produce very hot water, and in fact UK legislation actually requires water to be heated to temperatures of 60-70C to kill dangerous Legionella bacteria. Ideally you’d want your solar panel to be colder than that.

You can get around this by using a heat pump to produce very hot shower water while pumping lower temperature water through your solar PVT panels. But that of course means additional expense – and much higher electricity consumption than the circulation pump of a normal solar thermal system. Also, it is worth pointing out that most PVT systems on the market today actually cost more than the combined cost of a conventional PV system and some solar thermal panels.

The Upshot: If you have enough roof space you’re probably better off installing separate solar PV and solar thermal systems.

2. Is there a case for thermodynamic systems? So-called “thermodynamic” systems (a fancy term that doesn’t really mean much) are essentially simple (unglazed) solar thermal panels connected to a heat pump. They haven’t been on the market for long enough for us to have good data, but there’s reason to be very sceptical. In the UK there simply isn’t much solar energy available in winter because days are short and the sun is low down and very often hidden behind clouds altogether.

Under those conditions, a “thermodynamic” system is essentially an air-source heat pump (ASHP) that relies on heat transfer from the ambient air to the solar panel. Manufacturers claim that the system will provide hot water at every time of the year – and that is probably true, but during dark winter days this energy is not solar energy but rather energy produced by a heat pump, which consumes a lot of electricity.

Furthermore, because the “thermodynamic” panels usually use a type of solar panel that’s less efficient than a normal (glazed) solar thermal panel, they’re probably also not a good choice during the sunnier parts of the year when a normal solar thermal system can produce hot water at a much lower electricity cost.

The Upshot: A large dose of scepticism is currently warranted when it comes to these systems. This is also reflected by the fact that their accreditation under the Microgeneration Certification Scheme (MCS) has been suspended, which means you won’t get Renewable Heat Incentive (RHI) income.

3. Are heat pumps right for me? The answer is “it depends”. Heat pumps use electricity to extract ambient heat (heat in the air or ground) and supply that heat into your house. Today most electricity is produced very inefficiently – for instance, our coal and gas power stations consume two or three units of fossil fuel heat energy for every unit of electricity they produce. If electricity from these inefficient power stations is used to run heat pumps, then these heat pumps need to be very efficient. Basically, your heat pump would need to supply three units of heat for every unit of electricity it consumed, otherwise you might be better off heating directly with oil or gas!

To work efficiently, heat pumps need to run at a relatively constant rate supplying heat at low temperatures. This is a realistic option for a (usually new-built) house that is well insulated and has underfloor heating with densely spaced pipes. In this case even when it is very cold outside the water in the heating system need only be lukewarm (maybe 30-35C). On the other hand, if the heat pump needs to supply much hotter water, for a badly insulated building or a building heated by radiators, then the efficiency of the heat pump will likely be too low to make it a good choice.

4. Micro hydro: yes or no? Hydropower is great, and if it benefits a whole community rather than one individual then all the better! Unfortunately, only a minority of communities in the UK have the kind of site that’s suitable for hydropower: A stream with a large flow rate of water and a good height drop. If you have a site of this type then it’s definitely worth exploring the option of installing a micro-hydro scheme.

5. Should I heat my house with biomass? Biomass can be a good choice, especially where wood can be sourced locally and/or for buildings where heat pumps would not work at high efficiency. But it’s important to stress that wood fuel is a limited resource and that there are potentially negative side effects to burning it (e.g. local air pollution from smoke, time lag between when CO2 is emitted and when a new growing tree absorbs it again). This doesn’t mean we shouldn’t burn wood, but it means we should try to use it as efficiently as possible. This means always reducing a building’s energy consumption first, and using the most efficient appliances available for burning wood. For example, modern log batch boilers (wood gasification boilers) get more heat out of the same amount of wood, and emit less smoke, than traditional wood stoves (or, even worse, open fires!).

Have a question about renewables and your home that we didn’t answer here? Check out our Home Energy Handbook, or give our Free Information Service a call!