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| Green Building Bible, Fourth Edition |
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These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
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Posted By: SimonDFor a moment I thought it might be covering the new Part L amendments to come into effect in June this year. Especially that newbuild and complete replacements of wet central heating systems will need to be designed for a flow temperature of 55 degrees C......................This does rather seem to be a quiet way to force industry towards system design suitable for future heatpump installation
Posted By: Peter_in_Hungary
IMO more likely a way to force condensing gas boilers to condense.
Posted By: djhWell if it does both that should be a good thing ... ?
Posted By: WillInAberdeenSection 5.4b of the new Part L prohibits you from switching away from a heat source that is defined as lower 'Primary Energy' such as a gas/oil/coal boiler and replacing it with a source defined as higher 'Primary Energy' such as an immersion heater powered by a PV panel.Hmm, dunno why I haven't read that before so thanks for prompting me
So you won't be able to electrically heat your water if you want to sterilise it above 55â°, you'd need to increase the temperature of your system boiler instead.
Interested to see if this is enforceable!
But I confess I lost the will to live in a lot of the details.Posted By: WillInAberdeenElectric immersion (any source) is defined to consume 1.50 kWh of Primary Energy per kWh of heat.I'd thought a resistance heater was 100% efficient?
Posted By: WillInAberdeenSolar power is defined to consume zero Primary Energy if it shines in through your window, but 1.501 Primary Energy if it shines onto your PV panels*.Are you sure about that? The example I looked at simply subtracted the kWh of generated power from the total used (to get the amount drawn from the grid) and then multiplied that by 1.501 to find the gross primary energy. Oh and it then subtracted 0.501 times the exported solar kWh in order to calculate the net primary energy used by the property. The example was somewhere in all the SAP documents; don't remember exactly where I'm afraid.
Posted By: WillInAberdeenIf you divert PV to displace gas water heating, then you increase Primary Energy consumption by 1.501 for the PV but reduce it by 1.130 for the gas savedThis is the bit I don't follow. If you divert more PV to heat your water then it is subtracted from your electricity grid import, thus reducing your primary energy by 1.501*whatever. Your gas primary is also reduced, so net win all round. What am I not seeing?
Posted By: djhPosted By: WillInAberdeenIf you divert PV to displace gas water heating, then you increase Primary Energy consumption by 1.501 for the PV but reduce it by 1.130 for the gas savedThis is the bit I don't follow. If you divert more PV to heat your water then it is subtracted from your electricity grid import, thus reducing your primary energy by 1.501*whatever. Your gas primary is also reduced, so net win all round. What am I not seeing?
Posted By: SimonDI'd largely agree that: the energy generated inside the house boundary is subtracted from that imported and the exported energy is also subtracted but at a value of 0.501Yes, I'd forgotten the reduction in export. So if it's new PV you install to power your diverter I think what I wrote is correct. If you're adding a diverter to an existing installation with PV then the export is reduced as well as the change to import, so the advantage is only counted with a factor of 1 (1.501-0.501) instead of the 1.501 I used. But it's still a reduction both in electricity PE and gas PE.
Posted By: WillInAberdeenNo, PE is consumed whenever a 'natural form of energy is converted by a human process '(by definition). If you added extra solar panels, you are consuming more PE.Compare Dwelling C with Dwelling D as before.
Likewise you can't build an uninsulated house off-grid, heat it with a huge PV array, and claim you are not using any PE.No you're consuming exactly as much PE as the panels generate. But in SAP your 10,000 kWh heating demand is met by 10,000 kWh PV and the primary energy reported in SAP is 10,000 - 10,000 = 0. [adjust the PV generation in Dwelling D to confirm)
but ...Posted By: WillInAberdeenNo, PE is consumed whenever a 'natural form of energy is converted by a human process '(by definition). If you added extra solar panels, you are consuming more PE, irrespective whether you export the electricity or not.A couple of quibbles:
PE is a weird concept, it's not like ordinary energy which cannot be created or destroyed. If you convert sunlight into electric heat then you consume PE.PE is just like ordinary energy. It is ordinary energy. The sunlight is the PE, and it can be converted into electricity. You only effectively consume it when you consume the electricity, as you say, when you convert the electricity to heat. The chemical energy in gas is the PE and again it is consumed (i.e. converted to heat) when you burn the gas. Energy is conserved. PE is no more weird than the quantity of electricity or gas that exists at any one time.
Posted By: methe House A in the BRE doc ...... would score better than the PV+panel-heated House D, despite having higher CO2 emissions.
You could legally build the gas-heated house A, but you couldn't subsequently convert it to panel heaters (House C or D), both of which are better for the environment.
Posted By: WillInAberdeenAD-L s5.4bii...All bonkers.
Posted By: WillInAberdeenIf PE were conservedWhy should PE be conserved? Mechanical energy isn't conserved, electrical energy isn't conserved, thermal energy isn't conserved, acoustic energy isn't conserved, nor any other type. So why would you expect wind to be conserved, or sunlight? It's the sum of all the different types that is conserved.
if the sun shines on a PV farm which delivers 1kWh electricity (1kWh PE by convention)No. The PV farm generates 1 kWh of electricity (which is not PE, it's a secondary energy) using (by convention) 1 kWh of PE (sunlight). In practice solar panels aren't 100% efficient but the efficiency doesn't really matter since sunlight is effectively infinite so the accounting convention says that the PE factor is 1.0. The rest of the sunlight is dissipated as heat and doesn't get counted. All that happens is that electricity gets counted whilst a direct conversion to heat doesn't. But if the sunlight falls through a window and heats the building directly then it does get counted, as solar gain. It's not a question of conservation, it's simply a question of where the boundaries get drawn for an accounting of a building's energy use (and for the wider world's energy use).
A) if you insulated House A so it uses half as much energy, and then fitted panel heaters, the SAP PE and CO2 scores would be better than for the gas-heated house. This seems like a good idea, but would be illegal because panel heaters "have a higher primary energy demand per kWh of heat" (AD-L s5.4bii)Well as Simon says, you can as long as you reduce heating to less than 25 kWh/m²a (i.e. EnerPHit level) which seems a reasonable goal for a retrofit to me.
B) If we run an electrolyser to make green hydrogen with some losses, the PE factor of the hydrogen will be correspondingly greater than that of the electricity, which is already greater than that of gas. So a hydrogen-heated house now scores less favourably under AD-L than burning gas or using panel heaters. It is illegal to convert a gas boiler to burn hydrogen (S5.4bii again).It depends what electricity you use of course, but for grid electricity you're right I believe. But what would be the point of doing that instead of using an electrical boiler or cooker? Why would you want to burn hydrogen, or anything? If you somehow got hydrogen sensibly, then use it in a fuel cell. Hydrogen gas mains for Joe Public is a nonsense, IMHO.
C) if by 2050 the electricity supply will be 80% wind/PV and 20% nuclear/CCS/hydrogen/storage, the PE factor of electricity will work out in the region of 1.4.Sorry, but where does that number come from? My google-foo isn't finding it.
All bonkers.Absolutely stark, raving bokers. Agreed. ADL1 is now a very distressing document.
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