Author Topic: Electricity/Heat micro-generation  (Read 891 times)

fd3

Electricity/Heat micro-generation
« on: July 03, 2019, 10:48:32 am »
I'm interested in micro-generating electricity (though I don't think it's within the budget).  Things change quite quickly but last time I checked micro-wind is impossible, so it needs to be PV panels.  We have a section of roof that is flat and a section that is south facing - but the last time I contacted a company for a quote their automated system told me that it would not be worth it.  Has anyone got some experience with PV?
An alternative would be a smaller array for water heating, but I don't know that that would work in tandem with a combi boiler.

We may need to concrete the floor in one of the downstairs rooms, at which point I would be interested in the option of fitting a heat pump.  Again I am concerned that the cost would be prohibitive - has anyone had experience of these?
[/I could be wrong]

Kim

  • Timelord
Re: Electricity/Heat micro-generation
« Reply #1 on: July 03, 2019, 11:09:08 am »
You can heat water and feed lukewarm water via a mixer valve to the input of the combi (or, presumably, pissy landlord electric shower, washing machine, etc), reducing the amount of work it has to do to reach the desired temperature.  Barakta's parents had such a system in their previous house.  I'm suspicious it was a bit of a scam, but the technology worked.
To ride the Windcheetah, first, you must embrace the cantilever...

simonp

  • Omnomnomnipotent.
Re: Electricity/Heat micro-generation
« Reply #2 on: July 03, 2019, 12:18:01 pm »
I'm interested in micro-generating electricity (though I don't think it's within the budget).  Things change quite quickly but last time I checked micro-wind is impossible, so it needs to be PV panels.  We have a section of roof that is flat and a section that is south facing - but the last time I contacted a company for a quote their automated system told me that it would not be worth it.  Has anyone got some experience with PV?
An alternative would be a smaller array for water heating, but I don't know that that would work in tandem with a combi boiler.

We may need to concrete the floor in one of the downstairs rooms, at which point I would be interested in the option of fitting a heat pump.  Again I am concerned that the cost would be prohibitive - has anyone had experience of these?

We have no useful south facing roof but that isn't a barrier. We have an east and a west facing roof, so we use both. The system is so far producing more output than predicted.

The loss of the feed-in tariff is a shame. However already at least one electricity supplier is offering to buy electricity at the FiT export rate (roughly 6p/unit).


Re: Electricity/Heat micro-generation
« Reply #3 on: July 04, 2019, 10:19:01 pm »
there has been much talk of micro-CHP using stirling engine technology in the past, but I don't know if such systems are currently available/feasible or not.

cheers

Kim

  • Timelord
Re: Electricity/Heat micro-generation
« Reply #4 on: July 04, 2019, 10:23:27 pm »
there has been much talk of micro-CHP using stirling engine technology in the past, but I don't know if such systems are currently available/feasible or not.

High-temperature[1] fuel cells seem like a more promising way to do it; fewer moving parts, no loss of working fluid, etc.  This sort of thing:  https://www.viessmann.co.uk/products/combined-heat-and-power/fuel-cell

It seems like an efficient way to use gas.


[1] The type that are established tech, but impractical for powering a car on account of all the waste heat.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Electricity/Heat micro-generation
« Reply #5 on: July 04, 2019, 10:27:12 pm »
I had a mate who was doing his PhD on small gas turbines for home CHP installations 15 years ago; IIRC it was close to economic viability then, but I've no idea how the changes in renewables more generally have shifted the incentives.

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Electricity/Heat micro-generation
« Reply #6 on: July 06, 2019, 08:00:40 pm »
we make money from ours, not as much as my parents who got a better FIT than us.

Depends what you want to do, just offset use of electric from the grid, or get money back from the FIT.   Remember that the FIT pays out regardless of wjhat you actually send out, so we use it to run the immersion heater if there are any spare elctrons, and tend to run the tumble dryer when it's sunny.

With a south facing roof, are they saying you won't generate, or just won't make money?
“Procrastination is the thief of time, collar him.” –Charles Dickens

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Electricity/Heat micro-generation
« Reply #7 on: July 06, 2019, 08:01:43 pm »
I had a mate who was doing his PhD on small gas turbines for home CHP installations 15 years ago; IIRC it was close to economic viability then, but I've no idea how the changes in renewables more generally have shifted the incentives.

They've also been talkin about modular pebble bed nuclear reactors on a neighbourhood scale for the same length of time, and that's no nearer reality either.
“Procrastination is the thief of time, collar him.” –Charles Dickens

Re: Electricity/Heat micro-generation
« Reply #8 on: July 12, 2019, 10:12:06 am »
Your answer depends on what your objectives are: going zero carbon, capability of operating in "island" mode off grid for a short while, or just reducing your energy bills a bit.  Quick thoughts (happy to expand or take up conversation via PM)

Firstly - invest in energy efficiency.  This is almost always the cheapest way of reducing your bills.  LED lights, A++ rated appliances, timer controls, etc.  Worth investing £20 in a plug in power monitor so you can see how much juice your appliances actually use. It's enlightening - see July edition of The Energyst magazine, pages 50-51, for my article on the subject (although note the bloody editor dropped a zero off one of the numbers in Figure 2 :facepalm: )
https://theenergyst.com/the-energyst-magazine-latest-edition/

* Micro CHP - unlikely to be useful.  Various different technologies have been tried, including stirling engines, and there may be some still available.  However, the basic premise is that you can do something with the heat being generated in order to keep them running long enough to offset a good chunk of your electricity demand.  This may suggest you'd want a decent size thermal store to allow the CHP to run-on a bit and stop it cycling on an off.  It may be worthwhile if you have a hot tub you want to drop waste heat into.  Generally, the technology is complex - there are few of them about, and long-term servicing availability may be tricky.

* Heat pumps.  These fall into various types.  Ground source (GSHP) are likely to work out very pricey for most folk due to the need to install ground loops or a borehole (or 2).  Air source (ASHP) though are within the realms of possibility, and the new 3rd generation systems can operate fairly efficiently at higher output temperatures.  Nonetheless, they do work far more efficiently at lower output temperatures and are better suited to properties where you have underfloor heating and where the property isn't ancient and leaks heat all over the place.  You can get hybrid heat pumps which work alongside a small gas or oil boiler, so the heat pump does the baseload low temperature stuff using grid electricity (which is become less carbon intensive rapidly), and then top up with the conventional boiler for peak load work.  It adds complexity and space requirements to the installation.
ASHP/GSHP attract domestic renewable heat incentive (RHI) payments for 7 years for the renewable part of the load - up to a capped limit, but for the right property you could get a good chunk of your investment back.  Additionally, the RHI rules now allow you to re-assign your RHI payments to a 3rd party, so there are folk out there who will part of fully fund your installation and bank your RHI payments which alleviates the up-front capital strain.  Requirements include that both the kit and the installer are accredited by the Microgeneration Certification Scheme.

Solar PV - for a flat roof or east/west orientation expect to lose 10-15% of optimal generation, but you should still yield perhaps 800 - 900 kWh per kW peak generation sizing per annum (e.g. 4kW array x 800 = 3200 kWh/year), of which you'll probably use 35 - 50% on site and spill the rest to grid.  There are some great smart controls out there which work to utilise your generation on site (e.g. by switching on/off your immersion heater, or an EV charger) to avoid spilling to grid.  (see myenergi.com for examples).  PV would be ideal if you also have a heat pump (although peak PV generation is in the summer/peak heat pump electrical demand is in the winter) or if you have an electric vehicle to charge.  Expect the inverter to need replacing any time after about 7-10 years, but the panels should be good for 25+ with some performance degradation over time.

Solar thermal (hot water).  Can contribute 100% of domestic hot water even on not particularly sunny days, but payback is fairly long - especially if you currently have gas heating.  I have solar thermal, controlled to work alongside my wood pellet boiler, and it does a great job reducing the summer demand on the boiler, and still makes a contribution on sunny winter days.  Not sure if solar thermal still attracts domestic RHI payments.  I know I'm getting RHI for mine but it was installed 5 years ago.

There are other technologies out there too.  Forget small wind power.  It only gets economic on sites with clear wind flow (i.e. not right next to a house!) and at larger scale (say 15kW and up), so best suited to farms and the such like.

DON'T FORGET SERVICING COSTS!
A typical gas/oil boiler costs around £50-100 to service each year depending on location and whether or not your engineer is VAT registered.  My wood pellet boiler costs £380 a year to service!  Heat pump service prices are currently in the realm of £300 including VAT per year although you can probably get away with servicing less frequently (although should still have pressure vessels safety checked).  Any RHI payments help offset these costs for the 7 years but once the RHI stops paying out you could be left with increased service costs.  I think heat pump servicing costs will drop very rapidly once the RHI gets canned and once the forthcoming ban on new installations of fossil fueled boilers comes into play in a few years.

Hope that helps.  Others OTP should have further insight.  Paging Mr Woofage....

Re: Electricity/Heat micro-generation
« Reply #9 on: July 12, 2019, 02:46:04 pm »
 I have solar electricity generation and this keeps my hot water during the daytime. I also have a plug-in hybrid golf which sits on the drive probably five days out of seven as I cycle to work. Is there any way of using the battery To store energy from the system? Should I set the charging to only happen in the day time?

Re: Electricity/Heat micro-generation
« Reply #10 on: July 12, 2019, 04:10:43 pm »
@chrisbainbridge

yes!  https://myenergi.com/product/zappi/ is probably your solution
However, a quick Google of the VW Golf hybrid battery size suggests it's around 8.7kWh storage.  Doing some quick maths with assumptions:

* grid electricity = 15p/kWh
* PV generated  = 0p/kWh
* car battery full discharges per week, maximum twice therefore total demand = 17.4kWh for battery charging.
17.4 x 15p = £2.61/week avoided cost.
HOWEVER
that assumes that you're currently charging on a single rate tariff rather than using an EV specific tariff or a fully flexible tariff like Octopus Agile.
it also assumes that you can fully charge and discharge the battery using the PV on consecutive day. 
It sounds like you would only use the car weekends, therefore it's more likely you would part discharge and part re-charge the battery.  This is less likely to achieve much in the winter when the sun shines less, so actual savings would be lower.  Now compare that to the cost of a smart charger like the Zappi, and it starts looking like a very long payback indeed.  The Zappi comes into its own when you have a big PV array (up to 4kW peak) and a fully electric vehicle.
Also, I note you currently use the solar PV to heat water (using immersion heater presumably) which would diminish the generation available to charge the car.
C
[edit to add that I have no commerial link to any of the companies mentioned above!]

Re: Electricity/Heat micro-generation
« Reply #11 on: July 12, 2019, 07:18:57 pm »
So I should have bought the Tesla🤗

Thank you. I will have a look. May be better next year when we plan on perhaps a Polestar.

simonp

  • Omnomnomnipotent.
Re: Electricity/Heat micro-generation
« Reply #12 on: July 12, 2019, 09:32:23 pm »
I'm considering a fixed storage battery which can save energy all the time whether there's an EV at home or not. If we add some extra solar capacity at the same time we could have the reduced VAT rate for now, which means the extra solar could be almost free. We currently have 8kW max output - I suspect a 2-3kW additional array could be fitted on the garage roof. That would take total capacity to 16kW (5kW battery, 3kW solar on top of the existing 8kW), we'd need to get a further G85 permission. That might well be refused. But if your car can feed back to the grid, does that not require permission also?

If I had an EV with decent range I'd try to work from home on sunny Wednesdays. Something like a TM3 could easily do round-trip commute twice on a charge so charging at the weekend and midweek could work nicely.

Re: Electricity/Heat micro-generation
« Reply #13 on: July 15, 2019, 11:49:05 am »
I'm considering a fixed storage battery which can save energy all the time whether there's an EV at home or not. If we add some extra solar capacity at the same time we could have the reduced VAT rate for now, which means the extra solar could be almost free. We currently have 8kW max output - I suspect a 2-3kW additional array could be fitted on the garage roof. That would take total capacity to 16kW (5kW battery, 3kW solar on top of the existing 8kW), we'd need to get a further G85 permission. That might well be refused. But if your car can feed back to the grid, does that not require permission also?

If I had an EV with decent range I'd try to work from home on sunny Wednesdays. Something like a TM3 could easily do round-trip commute twice on a charge so charging at the weekend and midweek could work nicely.
A fixed storage battery won't "save" energy but will store it for use later, albeit with some losses resulting from conversion from DC (PV output) to AC (via inverter) to DC in the battery and then back to AC for main usage.  Not sure if there are batteries out there which will take the DC output directly from PV, albeit at a regulated voltage?
I should think you'll need to get the G85 permission updated, and the distribution system operator may require additional relays/witnessing fee etc as part of the installation.  G85 is partly there to ensure the local grid voltage isn't adversely affected but also to ensure that in the event of a power outage on the grid, the DSO (and any electricians working in your house) are aware that there could still be a live feed into the network.
As you suggest, a vehicle-to-grid feed would also need notifying to the DSO, as would addition of heat pump loads.  This should help:
http://www.energynetworks.org/electricity/futures/electric-vehicles-and-heat-pumps.html

simonp

  • Omnomnomnipotent.
Re: Electricity/Heat micro-generation
« Reply #14 on: July 15, 2019, 11:57:52 am »
I'm considering a fixed storage battery which can save energy all the time whether there's an EV at home or not. If we add some extra solar capacity at the same time we could have the reduced VAT rate for now, which means the extra solar could be almost free. We currently have 8kW max output - I suspect a 2-3kW additional array could be fitted on the garage roof. That would take total capacity to 16kW (5kW battery, 3kW solar on top of the existing 8kW), we'd need to get a further G85 permission. That might well be refused. But if your car can feed back to the grid, does that not require permission also?

If I had an EV with decent range I'd try to work from home on sunny Wednesdays. Something like a TM3 could easily do round-trip commute twice on a charge so charging at the weekend and midweek could work nicely.
A fixed storage battery won't "save" energy but will store it for use later, albeit with some losses resulting from conversion from DC (PV output) to AC (via inverter) to DC in the battery and then back to AC for main usage.  Not sure if there are batteries out there which will take the DC output directly from PV, albeit at a regulated voltage?
I should think you'll need to get the G85 permission updated, and the distribution system operator may require additional relays/witnessing fee etc as part of the installation.  G85 is partly there to ensure the local grid voltage isn't adversely affected but also to ensure that in the event of a power outage on the grid, the DSO (and any electricians working in your house) are aware that there could still be a live feed into the network.
As you suggest, a vehicle-to-grid feed would also need notifying to the DSO, as would addition of heat pump loads.  This should help:
http://www.energynetworks.org/electricity/futures/electric-vehicles-and-heat-pumps.html

You can have DC-coupled battery storage, but we'd go for AC-coupled, this is easier to add to an existing installation.