Waves, weirs and waterwheels – unleashing the power of water

How can we use and manage water in a more sustainable way? CAT volunteer and MSc student Ed Macdonald has been exploring the issues and delving into the detail of hydro power.

Born in the year of the water dragon, perhaps my interest in watercourses is to be expected. As a kid in a nearby natural sandpit I was enchanted by flow of the stream, able to bypass attempts to dam it with clay. Fast forward 20 years, I found a refreshing challenge in designing water treatment facilities for schools in the Kenyan highlands with an NGO, which led me to CAT’s Graduate School of the Environment for further training.  Continue reading “Waves, weirs and waterwheels – unleashing the power of water”

World Wetland Day 2016

The Centre for Alternative Technology sits in the Dyfi Biosphere, a UNESCO world heritage site. We were give the status largely due to our proximity to Cors Dyfi, a unique peat bogland site.

map bach_0

Wetlands host a huge variety of life, protect our coastlines, provide natural sponges against river flooding, and store carbon dioxide to regulate climate change.

Unfortunately, wetlands are often viewed as wasteland, and more than 64% of our wetlands have disappeared since 1900.

Many of the short courses developed at CAT are done with the protection of the local ecology as a driving factor. We offer courses in Pond and Stream Invertebrate Life, Understanding Amphibians, Rainwater Harvesting, Greywater and Water Purification, Reedbeds and Waste Water Management and Ecosystem services:- Land use, water and waste management.


Join us on a short course and help us spread awareness about the importance of wetlands.

ZCBlog: The Story of Human Beings and Energy

Humanity’s relationship with energy presents us with some big challenges, not only for our technology, but also for our culture, society and democracy. In his recent article for Resurgence & Ecologist magazine, Paul Allen, the Zero Carbon Britain Project Officer, takes a look at how this relationship evolved and exactly where it went wrong.

The extraordinary story of humans and energy began over 400 million years ago with the formation of fossil fuels. For thousands of years human societies lived on their annual sunlight ration, until the discovery of fossil fuels, that had a massive effect on how we see ourselves and our relationships with our friends, family, communities and the natural world. On one hand such a transition brought us the incredible advances of medicine, science, education and entertainment. But on the other hand, we must now live with, or bury, the pain of the destruction, exploitation and capitalisation of our natural spaces and the people who inhabit them.

Although it has become a deeply pervasive source of anxiety, society has created taboos against the public expression of such anguish, leaving many paralysed, overloaded with information – sleepwalking through the shopping malls. Over time, this build-up of collective anxiety has transformed the way contemporary culture portrays our future: from an exciting new world of progress to one of darkness and uncertainty. Whenever contemporary culture looks ten or twenty years ahead, we now paint dystopia and ecological collapse.

Forest of oil wells in Signal Hill, California 1923
Field of oil wells in Signal Hill, California 1923

Yet if people can’t imagine a positive future, how will they create it? The Zero Carbon Britain project has been developed by CAT to help us to think differently. We must, of course, acknowledge that fossil fuels have enabled a fantastic transformation: fuelling the embryo of human society, much like the yolk of an egg fuels the development of the chick. But we know fossil fuels cannot go on forever, as burning them releases the massive amounts of carbon dioxide locked away when they were formed, and the peaking of conventional oil and gas supplies will also cause increasing turmoil in the economies and societies that still depend heavily on them.

Wind and Solar energy generation at CAT

The next chapter the story of humans and energy must begin now. Our tools for energy capture are now no longer limited to soil, canvas and wood; we now have an incredible array of renewable technologies that can capture enough energy from our annual sunlight ration to more than meet our global needs. The conclusion of the story of humans and energy is still unwritten, but is has become clear that our 21st century challenges can no longer be met with a 20th century approach, including how we think about the future!

Zero Carbon Britain – Rethinking the Future is available to download free of charge.

The full Resurgence & Ecologist article can also be found on their website.

Should Britain look forward to a new wave of tidal power?

Last week, an influential House of Commons committee announced serious concerns over Hafren Power’s proposed Severn barrage. It has been claimed that the facility could provide up to 5% of Britain’s electricity demand but critics warn that wildlife could be deeply affected. What does this mean for the future of tidal energy in the UK?

In theory, tidal energy offers huge potential for the UK’s power mix. Tides are incredibly predictable, more so than wind energy and solar power. But the sheer power contained in Britain’s seas come at a cost. The damage that seawater causes to materials and machinery makes maintenance an issue.

Tidal projects have always been difficult to fund, despite the fact that the UK has great locations for wave and tidal energy projects. The upfront cost of constructing these renewable energy projects has put many off. The other major downside to tidal barrages is the somewhat unpredictable ecological impact.

Peter Hain, former Welsh Secretary of State, has been a strong advocate of the Severn Barrage. Hain’s website states: ‘The barrage makes sense environmentally’. But is this really the case?

The current proposal is a 18km fixed tidal barrage across the Severn estuary. MPs on the energy and climate change parliamentary select committee have been examining the proposal. The report said that while a barrage might help tackle climate change, the environmental and economic case is not strong enough. The committee did however urge the Government to consider developing smaller tidal facilities.

Hafren Power responded to the report by saying ‘We believe the environmental and economic issues can be solved with everyone working together’. They claim that the Severn Barrage will protect against storm surges and save the UK billions in flooding costs. Critics, such as RSPB and WWF, fear that it will endanger the ecosystem, particularly birds and fish.

Peter Hain claims ‘the Rance Barrage in France suggests that there would be a significant increase in faunal abundance and biodiversity. The barrage would slow down the fearsome Severn tide, introducing more light and oxygen and therefore improving the water quality, attracting more fish which will support greater and more diverse birdlife.’

The Rance Barrage is one of the biggest tidal power stations in the world. Development costs were extremely high but these have now been recovered and it produces around 600 GWh a year.

Research shows that the dam has clearly modified the currents of the estuary and caused progressive silting. Sand-eels and plaice have all but disappeared, though sea bass and cuttlefish have returned. There have been large changes to the aquatic ecosystem of the Rance estuary but it continues to be varied.

So what about alternative schemes in the UK?

The Swansea Bay tidal lagoon is one such project. An ambitious tidal power station, it is seeking £10m of funding from the public. The scheme claims it could power 107,000 homes and generate 250MW of renewable energy. Small-scale investors have being offered a 55% stake in the company.

Traditional barrage designs consist of two different types. Ebb generation allows water to fill an enclosed area until full tide. Once the sea level has fallen enough, to create sufficient head, turbines generate power from the water leaving the enclosed area. Two-way generation allows water to flow through the turbines as the tide goes in and out. This energy produced is usually less than ebb generation but electricity is produced over a longer period.

The Zero Carbon Britain report recommends that tidal and hydro should supply 4% of the UK’s energy.

Tidal energy is still in its infancy compared with wind and solar, which have a proven track record. But with the crown estate investing £20m in the UK’s wave and tidal energy, this industry could soon begin to contribute. Ongoing advances in designs like SeaGen and VIVACE mean that the UK could be on the crest of a new wave of possibilities.

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!


ZCBlog: Tips for community energy schemes

Last week the chief executive of Ofgem warned that Britain will come “dangerously” close to power shortages within two years. Community energy schemes are a great way to guarantee energy security and ease the strain on our energy system.

Some groups have responded to Ofgem’s power warnings by calling for more nuclear or shale gas, or for an end to ‘green taxes’. However, only by living more economically within our resources can we hope to protect our communities, environment and climate.

By reducing the energy demand of Britain’s communities we can all protect against fuel poverty. Community renewable energy (CRE) projects can enable anyone to reduce both their carbon emissions and their energy bills!

There are other benefits as well. A successful CRE project can bolster local resilience and build a sense of empowerment. Community schemes can create jobs and training as well as boost local economic development.

Community renewable energy projects are not easy to set up, but if done properly the long-term rewards are well worth it. Here’s some tips to get you started:

  1. Have patience! CRE projects need dedication because they will take a long time. The odds are someone in your community will oppose the plans, legal and governance regulations can also take their toll, but if you are passionate and can show the benefits then you will convince others.
  2. Make sure the location fits your vision. There’s potential for community energy schemes everywhere, but make sure it’s the right renewable energy. Solar PV is great in sunny urban environments, while wind is at its best at rural and coastal areas. Hydroelectric has massive potential, but finding the right circumstances is key to success. Check here for listing of MCS companies that can act as consultants. And don’t forget that district heating schemes can be a viable alternative when CRE projects aren’t feasible.
  3. Check your connection to the grid. Electricity grid connections are the responsibility of the local Distribution Network Operator (DNO). It’s a good idea to make contact with the DNO long before you formally request connection because this can ease the process and let’s you know what the. You also have to decide if you are going to export your power back to the grid or sell the excess power to adjacent properties, which will require a Power Purchasing Agreement.
  4. Make sure you do your homework. A feasibility study of your CRE project will determine if it is realistic, and help you plan your way. These studies are technical documents designed to take the project beyond the early planning stages and outline a proposal that can be used for funding. You can then take this vision to bodies like the Environment Agency and local councils.
  5. Cultivate a great relationship with your contractors. You will need to appoint a project manager to deliver the construction, installation and testing of the scheme. There’s no substitute for first-hand experience so pick someone knowledgeable that can oversee the building stage and resist the urge to have a large group micro-mange the project.
  6. This is just the tip of the iceberg! But there is loads of information out there to help you get started, such as the Rough Guide to Community Energy and the Community Energy Hub from DECC. CAT runs a range of introductory courses to renewable energy and has a free information service here. The Guardian blog also has a great article chronicling a hydro-electric project near Lancaster.

ZCB suggests implementing small scale Solar PV projects because they are quicker than most to install and start running. The feed-in tariffs may not be as financially beneficial as they once were, but photovoltaics still offer a practical and quick way to produce energy. The majority of roof-top PV systems do not need planning permission, and 2kW should be sufficient to provide about 40% an average home’s total requirements.

Co-operatives and local authorities can also play their part by providing larger renewable energy projects. Once again, Zero Carbon Britain calls for solar PV as the short-term solution because any large-scale power plants will not be ready by the end of this decade.

Tomorrow, the Sustainable Architecture blog will highlight how the building industry should also play a big part in how Britain can power down for rapid decarbonisation.

Podcast: how should we meet our energy needs?

The average person in the UK uses 197 kilowatt hours per day – or 41 days worth of cycling. How can we meet this demand in a manner that is environmentally sustainable, and affordable? Adam Tyler, one of CAT’s renewable energy experts, gives an introduction to the different technologies available, and their associated costs and benefits.

Part one:

Part two:

You can stream the lecture here, or download the mp3 files for

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.


Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.


Previous podcasts

[blog cats=”217″ per_page=”3″ image_width=”150″ image_height=”200″ divider=”line” pagination=”false” meta=”false” wrap=”true” /]