Wednesday, April 14, 2010

Carbon Zero? where do Sunboxes fit?

14 April : This article is now a Permanent Page on the blog
There is a link between what I am doing with the wider issue of Sustainable Technologies, with the prospect of the year-2016 looming up closer.

In a nutshell: If we are to move to carbon zero (or 'carbon neutral') by 2016, I think this technology will be essential. It cannot be done solely by improving Insulation - this would only be Code 4. We also have to think about Systems, primarily for heating (in the UK environment).
Considering the three primary methods that avoid burning COAL/GAS/OIL, the Sunboxes could be a real benefit one of the key technologies that is going to work in future.

1. Sunspace - and high thermal mass, with heat reclaim (MVHR) powered by PV/wind - Hockerton style. That is very expensive in construction and can’t be applied en masse, and is not being copied, brilliant as it is. It is low density and very demanding as to site positioning and lifestyle. All houses have to face south with large conservatories and massive thermal construction underneath and earth-sheltered roofs to the north. Very few developers will build houses with a managed sunspace facing south, and earth roofs. In the wider housing industry, the conservatory business is doing well, but conservatories are not actively used for heating the house. (I designed and built a house in 1982 that had a heat reclaim system drawing heat from a conservatory. I must go back and look at it sometime.) I don't believe that the SAP calculation knows how to include the effect of a managed sunspace any more than it does a sunbox augmented heat pump.

2. Biomass - wood burning – it might be theoretically 'carbon zero', because the wood was grown in your own lifetime. But it still involves burning and emitting smoke particles, and can’t be employed en masse for population, smoke and forestry reasons. It is a great back up to a primary heating system, but not for dense urban areas. There is massive work required in cutting up logs and pallets, and cleaning out the stoves etc. You can have wood delivered as special woodchips, which works well in Austria/ Switzerland. But if your woodchips are transported a long distance, consider 'chip-miles'.

3. Heatpumps – as used in over 90% of new houses in Sweden – surely, this is going to be the answer, because being powered by electricity, their fuel source can be generated by hydroelectric, nuclear, PV, wind etc. , and efficient heat-pumps can manage heating and hot water. There are new Feed in Tariffs coming in in 2011 to incentivise more use of Heatpumps. The heatpump uses some electricity to get vastly more heat from a warming medium - the air, water, the ground under or near the house..... Or in my case uniquely, a hybrid of Ground, Air and Solar.

[4. I have not included CHP (combined heat power) in this discussion because it burns fossil fuel. But see another article on this, because there can be benefits.]
[5. I have not included Carbon Offsetting, as that is just a procurement decision, and not about the design of buildings or systems. On this offsetting basis we are already Carbon Neutral because we buy energy from Good Energy's wind farms. We could be irresponsible, and live in a badly insulated brick house with electric fan coil heaters and falsely claim to be 'Carbon Neutral'. See Glossary.]
[6. I did not include Solar Thermal in the list because this mainly applies to Hot water, not to house heating. But my friend Karina Wells has a water tank that is heated by solar thermal and contributes energy-saving to the gas central heating system.]

So, let's discuss Heatpumps :-
Electricity is too expensive to use One-to-One, so a One-to-Three or One-to-Four conversion ratio is a way to stretch it further - by burning one unit of electricity in a pump and fridge unit, you hope to get 3 more from a heat source like Air, Water or Ground.

Air source is good, expecially if the existing plumbing makes it easier for them to be a 'boiler replacement' in existing buildings. They are working in an almost infinite flowing source. But in cold climate winters, air source is not so good - even in our mild climate they may use the immersion heater function too often. They are somewhat noisy for houses close together. They are used more for retrofit, and Ground source more for newbuild.
Water source is very good for those with access to river, lake or plentiful groundwater - not a solution for en masse housing, and so rare that there is not even a Wikipedia page about water source HPs. Running water is better - if you drew heat from a static water source such as large rainwater storage tanks, there is too high a risk of freezing.
Ground source works well in cold or hot climates, if you can face the initial cost of laying the pipes or boreholes. To my experience, ground source has the problem of declining ground temperatures and surprisingly high electric consumption. GSHP has a high cost for en masse use unless made more efficient. In a dense urban area, there isn’t enough land for horizontal ground source, so deep boreholes become necessary, despite the cost. Is there a way to make these more efficient?

   Ideally, you would ALSO have Solar thermal panels for Hot water but it is difficult to adapt this for heating! Solar Thermal needs a large tank and is expensive. Thermal panels can significantly augment the process of Water heating even for a ground source heatpump - but will they help with House Heating? Well they will if you use a ground source heatpump as your 'thermal manager'.

So I ask: 
Why not use solar panels to heat the warming medium used by the GSHP? What if we can use Ground source, but get the Solar heat down immediately into the ground? Do it This year, NOW! not wait until Ten years later? The Sunboxes show a way to do this.

Solar heat falls on the ground to replenish the deep soil temperature, but becomes less effective in urban areas because the ground is closely covered with highly insulated houses, or green landscaping that shades the ground… not enough tarmac or open space. By the way, next to our house in Nottingham, there is plenty of tarmac and open field, so solar heat does get down, but would not if everybody was doing it. Even if it does work, it takes decades to get down 50-100 metres.

If clusters of houses are all drawing heat out and not putting any down, that is unsupportable in the long term. On the other hand, if the clusters of houses are also pumping solar heat day-by-day deep into the ground, winter and summer, using Sunboxes, you don’t need acres of tarmac around to pick up the solar heat. The denser the houses (and well insulated in their slabs) the more likely that sunbox-captured solar heat is to stay down below where it is wanted.

How about 'Energy Foundations', where the HP draws heat from immediately under the building? Can this be done? Well my team are designing a colony of houses doing just this! Sunboxes pumping heat into the foundations, and Heat Pump getting it out again.

So you could be witnessing something significant.

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