pdf27

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  1. Much more important for the panels than the inverter, assuming they're roof-mounted. Installation costs are a big fraction of the total cost (scaffolding, etc.) and that is only going to increase as PV panel prices come down.
  2. "Construction Manager" (#1122) is on the shortage occupations list (https://www.gov.uk/government/publications/skilled-worker-visa-eligible-occupations/skilled-worker-visa-eligible-occupations-and-codes), as is "Builder" (#5319) so it will be possible to get a visa. You need to get approved as a sponsor before he can apply - that costs about £500 - and once you have it you can sponsor him to apply for a work visa.
  3. That's probably the one area that the Mixergy tank makes any sense, and only if you don't use the external plate heat exchanger. With PV your cheap electricity will be during the day in summer and night in winter, and just using an immersion at 5p/kWh (PV export cost) is relatively expensive. Heating from the bottom (or using the plate heat exchanger) means you de-stratify, and if you've got a relatively small heat pump (matched to a well-insulated house) you're going to have lukewarm water for some hours in the middle of the day. However, for all their "smart" controls and integration with Octopus Agile they have no ability to use PV for anything but an immersion. That's a major failing, and means you've got to be willing to write your own control system to really benefit from the increased cost & complexity (which to be fair is pretty minor in the grand scheme of things).
  4. https://www.topcylinders.com/mixergy-300-litres-standard-smart-hot-water-cylinder has it at £1150, which includes the control box.
  5. The standard version has a single (smallish) coil at the top which is in the hottest water. That gives a worse COP compared to standard type coils, which is why they do the external plate heat exchanger which can pull in colder water. So you can use it direct with an ASHP, but are likely to see a performance hit. Having said that, charging from the top will give much faster recovery so it is probably quite a good match for a big tank/small heat pump.
  6. It's less valuable than you'd think - you're very unlikely to be able to use it yourself, so even if you're getting a very good export tariff (5p/kWh) it's worth maybe £40/year - £400 over 10 years before cost of capital is allowed for. I'd expect the cost difference in the inverter to be pretty small (~£80 on Midsummer Wholesale) so if your DNO permits it does make sense to fit a matching inverter, but the value of doing so really isn't very big. It's also worth noting that the calculation is for a south facing ground mount - i.e. the conditions that give the best return on investment for matching inverter and solar panel size. For most real-world situations, the difference will be significantly smaller and you may even get more output from an undersized inverter because it will perform better at low power levels.
  7. Not exactly - it's more of an issue that the mechanical inertia in a wind turbine is fairly small. Good article explaining it here - https://spectrum.ieee.org/energywise/energy/renewables/can-synthetic-inertia-stabilize-power-grids . Combined with batteries it's likely to produce a good solution. Note that it's also possible to have a synchronous wind turbine if you really want it - go for something like a doubly-fed induction generator and you can tie the main stator directly to the grid. There are reasons it isn't the preferred architecture, but it isn't a dead duck. There is an issue with response time for batteries - grid inertia produces an inherently instantaneous response, which is quite difficult given the battery chemistry. It's less challenging but non-trivial to achieve the same with non-synchronous sources like wind turbines. Having said that it's quite likely that giant flywheels may be the cheapest way to add what is effectively inertia to the grid - they're cheap up front, cost peanuts to run and reduce the system costs associated with providing the inertia a long way away from your loads.
  8. Using Sunny Design, a 5.05 kW ground mount system with a 3.6kW inverter would give you 4377 kWh/year. Increasing it to a 5kW inverter gives you 5140 kWh/year, so about +800 kWh more per year. That's for a pretty ideal south-facing system - if you're roof-integrated and off due south then the optimum sizing will change a bit.
  9. Not especially - burning hydrogen in CCGTs is a much simpler solution than burning it in domestic boilers, since the ASHPs in the middle reduce the total hydrogen demand by a factor of ~3. Infrastructure costs on the grid are vastly lower too, while ASHPs aren't vastly more expensive than domestic boilers. At a system level, it's probably quite a bit cheaper.
  10. Only if they use the original radiators. Fit correctly sized radiators and it's fine. One thing that will need care - the insulation on the storage heaters needs to be much better than in ones that were made historically, otherwise you're likely to have issues with overheating early in the heating period and under-heating later. Once the insulation is good enough, you can probably get away with direct heating when power is cheap rather than storage heating - and the window between storage heaters not working and not being necessary is probably quite narrow. Probably maintenance rather than refuelling. Peak demand on the grid is actually very peaky - the last GW only needs to be provided for a few tens of hours per year - and diesel generators and/or batteries are a very good solution to this. They're unlikely to be constantly refuelling them though - maintenance is possible, but even that should be pretty limited. The economic attraction compared to power stations is that they're pretty much fit-and-forget, so the man-hours needed to keep them going should be pretty low. In a well insulated house, yes - provided that the time constant of the house is long enough, you can use the whole house as a storage heater. Essentially that's what TerryE is doing.
  11. Headache with that is that as soon as you've got a bit of hydrogen it's really easy to burn it in gas turbines to cope with nil-wind days. Using hydrogen for heating as well means vastly more wind turbines are needed than heat pumps with hydrogen backup for the grid during calm periods - it's a very expensive solution as a result, unless you derive it from fossil gas.
  12. Nope - persuade wealthy people to invest their money in a company which is extremely unlikely ever to make any money. They'll lose their investment, but the (less wealthy) people running the company will get a good living out of it for a few years.
  13. Wasn't it also an unventilated cupboard?
  14. Crudely, you're unlikely to be generating PV at the same time as your thermostat will be calling for heat. Most of the year you're using the grid as a giant battery with a round-trip "efficiency" (ratio import:export costs) of about 30% on one of the better tariffs, more like 0% on one of the Big 6 tariffs. Views differ on what is worthwhile and isn't - personally I'd be reasonably happy with that system and cost, but I'd also be fine with a payback of >10 years and doing a fair bit of work on load-shifting and time of use tariffs. I certainly wouldn't consider it a good investment from a purely financial point of view however.