Carbon Cutters - Solar Thermal

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Running on Empty

Required reading:

Chris Goodall "How to Live a Low-Carbon Life"

Richard Heinberg "The Party's Over"

George Monbiot "Heat"

Required watching:

The Power of Community - How Cuba Survived Peak Oil - DVD

The End of Suburbia - Oil Depletion & the Collapse of the American Dream - DVD

The Revolution

This is a revolution. If you want to shut an airport then stop flying. Want an end to factory farming? Grow your own. An end to pollution? Change to renewables. An end to war & poverty? Microgenerate. Life for your childen? Stop needing oil. YOU have THIS Power. You do not need Government. Seize the initiative. Bring democracy to your community. Be an example to your children. Take responsibility. Change for good today.

Free Hot Water from the Sun

Solar Thermal is a very mature Technology that is already in widescale use. Our experience shows that when you tell people you have "Solar Panels" they immediately think you mean the type that heats your water instead of Photovoltaics. A good installation can easily supply half of a household's Hot Water requirements and that is in Northern Europe. Costs are somewhere between £2,000 to £4,000 per installation although it will be at the upper end of this for the more advanced (more efficient) designs.

Hence it is a quick and relatively cheap "easy win" for most householders. So why don't we all have it? Simply because it is still more expensive than our current 'cheap' gas and oil alternatives. Crazy isn't it? However, this, as we know, will soon change.

Solar Thermal

It is more productive to capture energy with Solar Thermal Technology that it is to do it with Photovoltaics. Efficiency is expected to be anything up to 60% by 2020. However, these panels are physically more bulky and remember, there is fluid flowing through them. They are part of systems that have to tap into a house's hot water system. It can require some plumbing and some moving parts. Hence it can be a bit more complicated that Solar Electric - even if it is far cheaper to install for the energy you get out.

So far 100,000 homes in the UK already has this technology installed. Older styles only consisted of a flat metal plate but the new technology uses a set of vacuum tubes as is illustrated on this page (above and below). These systems do not replace your Heating System but can supply most of your Hot Water needs during the Summer Months but very little in Winter. Be cautious of the sales brochures offering up to 70% savings on your hot water bill. Only six months of the year would supply enough energy to avoid using the conventional boiler. The panels can heat the water from 10 degrees Celsius up to 60 degrees Celsius or more. Some heat can be lost back into the environment if hot water is pumped from the hot tank back to the roof when it is cold outside however, modern controller systems prevent this.

Cash savings per year vary from £23 for a small house up to £94 for a large home. Since a larger home's installation costs only 16% more than the small one this means that the pay back is far better on the larger installs. Likewise the costs per tonne of CO2 averted is £170 GBP for the larger install versus £600 GBP for the smaller.

The most efficient evacuated tube solar collectors convert 70% of the energy falling upon it into heat. However the installation must face south (obviously in the northern hemisphere) and be tilted up by about 30 degrees (in the UK). Anything else will not receive the full amount of energy possible. Typical installations are between 2 and 4 square meters supplying 1680 to 3360kWh/year. In June this latter figure could supply 545 litres of hot water. We consume 50 litres per person per day. A Bath needs 80 litres whilst a shower only 30 litres. This is quite a lot of capacity but it would be a lot less with pumped showers.

Hence the amount of fossil fuel you save depends upon how much hot water you use and what time of year it is. A greedy household could save only 40% whilst the most frugal may save 90%.

Read this Book

ISBN 1 90217 529 8. Chris Laughton's "Tapping the Sun" - A guide to Solar Water Heating. Published in 2006 by the Centre for Alternative Technology. Although short it is densely packed with loads of information, pictures and diagrams. By the end of this book any novice will be well armed with every piece of information required to select their own installation even if they are having it installed by professionals. More here.

Millablog

We were very late in realising the advantages of Solar Thermal. When Daddy wanted renewable energy he had Photovoltaics installed. This is great but we now think that Solar Panels for heating our water would have been a good alternative. So, on our next house that is exactly what we will have installed.

Resource

Passive Solar

Anybody who has stepped inside a glass-house on a cold day, to find it lovely and warm, has experienced 'passive solar'. The glass-house didn't do anything - it was passive. No Heat Pump, no Solar Panels. Just heat trapped behind a layer of glass by the 'greenhouse effect' we are now all so familiar with. But how can we utilise this?

It is surprisingly simple. Most techniques apply to building new houses but existing homes can benefit. If you have a Conservatory you should already have found that in Spring and Autumn that it can become considerably warmer than the house it is attached to. You need only open the doors between house and conservatory. Of course a North-facing Conservatory isn't going to have this advantage. Hard to imagine many people building that though. Most will be east, west or south facing. As long as they capture the sun's rays then this will work.

The second thing that has to happen is that the conservatory must be separated from the house living space by well insulated doors. Good double-glazed, double doors are best (rather than sliding doors). To let the heat in you need the widest opening possible but, in the heat of summer, or the cold of winter, you need to isolate the Conservatory from the house. Some people make the Conservatory part of the house and have no doors - or just leave them open all year round. This is madness. In winter the Conservatory is just a massive heat exchanger sucking heat out of your house and dumping it into your garden. In the summer you'll probably get so hot you'll install air-conditioning - what a waste! Just for want of doors?

Let the heat flood into your house in Autumn and Spring. Keep the excess heat out in Summer and keep the warmth in in Winter. This gives you a massive free solar boost to your home warmth through six months of the year in Northern Europe. Be careful with the timing of the opening and closing of the internal doors. Open them when it is warmer in the Conservatory than the House. When the sun drops out of sight the temperature in the Conservatory will drop rapidly and suck the heat out of your house. So get those doors closed quickly. Likewise, don't open them too early in the morning - for the same reason. Enjoy.

References:	Mayer Hillman "How we can Save the Planet" Chris Goodall "How to Live a Low-Carbon Life"

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