Free solar panel discussion

John_Pierpoint

Cardew wrote: »

J

Even more efficient(if still not sensible!) is put our huge solar farms in Southern France or Spain*. Electricity could be sent to us via the big fat cable that runs under the Channel that supplies us with nice clean Nuclear electricity. That cable is rarely needed in daytime, so could easily be utilized.

There is an unbelievably huge investment needed to switch to zero carbon energy, we need to build a second national grid for a start as the present set up assumes the average home in many parts of teh country will draw less than 2KW on average. So local production might make some sense.
We cannot even mend the pot holes down my way, when eh Japanese can rebuild a motorway in a month..

The French interconnector seems to run a pretty well full capacity at the moment but perhaps that is because it is cheap and reliable - subsidised by those nice French people.
All the graphs and statistics any nerd could want are here in almost real time! (At time of posting we gave France a boost at lunch time)
http://www.bmreports.com/bsp/bsp.php#SummaryPage

ronlizpatsimon wrote: »

I only joined this forum today. I have read, with interest, about a quarter of the posts.
I noticed a few things of special interest;-

Hi Ron & Liz (?) welcome to mse - both of you

Someone remarked that solar panels might be more efficient in the future as global warming affects us. I believe that the opposite is true. The planet will be warmer due to increased pollutants in the atmosphere. Yes this equates to warmer air, but these pollutants will impede the solar radiation and so panels will be less efficient.

Yes and hot PV panels work less efficiently than cool ones given the same amount of sunlight.

Someone else advocated (due to economies of scale) that it was more economical to erect the panels in open countryside rather than on rooftops. This is generally not true because no allowance has been made to encompass the fact that countryside can be used for other purposes (crops or grazing). I don't think sheep would enjoy grazing on my roof tiles!

There are vast areas of moorland that would have nothing on them if it were not for the agricultural subsidies being paid - mind you I don't think it would do much for the tourist industry to make them look like black greenhouses.


Another remark of interest was that someone had worked out what gadget to use so that surplus energy could be diverted to an immersion heater. Surely no such gadget is needed. You just switch on the immersion heater and turn off the normal oil or gas boiler. Electricity for the immersion heater will automatically flow from your new system in such a way that if your panels are not producing enough power to power the immersion heater then the shortfall will be made up by drawing it from the mains.

Mains electricity on average especially in the day time, is less than
50% efficient - the majority of the energy has gone missing having been chucked up the cooling tower, into the local river/sea or heated the toes of the birds sitting on the wires. It is almost impossible to create a situation where the immersion can turn on and off depending on the excess voltage created in the wiring by the panels being turned up and down by passing clouds. (There is a gizmo called EMMA but it is expensive).
If a house has gas use that, if electricity use the night rate, when the RHI (renewable heat initiative) starts install solar thermal panels, if there is room on the roof and get a 6% annuity from the rest of us based on the power you are deemed to have saved.

ronlizpatsimon

Good Morning John,
Thanks for replying to my queries.

With your response to my final query (Power to Immersion Heaters); firstly, although you are correct about the loss of efficiency with mains power from the generating station; these losses are of little financial consequence to me. (Besides, as a bit of a twitcher; I like the idea of my feathered friends having their metatarsals warmed)

I still do not follow the logic of the EMMA system. I see how it works, but do not understand why its needed. I see that normally (without EMMA) any surplus energy I have is automatically fed to the national grid. However; if I leave the immersion heater switched on and it uses at least as much as my panels are able to provide it with; then there is no surplus power to be passed to the grid. Or, are you suggesting that any household appliance (toaster, kettle, immersion heater etc) which require more power than the panels are producing, will automatically only draw all its required power from the national grid and not from my panels?

Equaliser123

ronlizpatsimon wrote: »

However; if I leave the immersion heater switched on and it uses at least as much as my panels are able to provide it with; then there is no surplus power to be passed to the grid. Or, are you suggesting that any household appliance (toaster, kettle, immersion heater etc) which require more power than the panels are producing, will automatically only draw all its required power from the national grid and not from my panels?

I think the point is that even the most domestic powerful panels - generally 4kwp under the FIT scheme - will not produce the steady 3kw requirement for an immersion.

That said, there must be a point when it is better to use the immersion than fire up the gas boiler even if some power is being taken from the grid.

If my 3.29kwp system had a 'spare' 2kw, then if I had to use 1kw from the grid to power the immersion then I wonder if that would make financial sense rather than using the gas boiler.

ronlizpatsimon

Good Morning "Equaliser123"

Yes, it would depend on the amount still required from the national grid, taking into account the cost of a "unit of gas" as apposed to a unit of national grid electricity.

I note that you did not directly touch on the subject of the requirement, or not, of the fitting of a EMMA component

John_Pierpoint

Somewhere, much much earlier in this thread I think, about 9 months ago, I suggested fitting hot water tanks with a supplementary immersion (say 1kW from a small kettle) and turning that on using a time clock, if the weather when you are out at work in the summer looks promising, but here again it is a matter of effort and cost to save the cost of a tank of hot water a day.

Given that gas could be as cheap as a 5P a kWh and night time electric say 6p a unit (OK I know that turning on the boiler, just to heat the tank, won't achieve 95% efficiency in terms of useful heat.) full price electric or "average" price electricity at 10 - 15P cannot compete.

Remember that in theory every unit you use on site should be costing you 3p (perhaps more if you are lucky enough to have a meter going backwards;))

http://www.energy.eu/

John_Pierpoint

Underscore wrote: »

I ended up going with Tesco, so I got £150 in clubcard vouchers off the near 15k that I paid for the system - much happier than if I had rented the roof. Once the FiTs start to come in I will report back on how much I actually receive compared to estimates etc. The installation was smooth enough and I was happy with it.

Interestingly, the April WHICH? had a look at cavity wall insulations and asked Npower, Tesco, M&S and The Mark group for quotes.
The specification from all 4 was the same but the prices ranged from MG at £149 to £249 from M&S with the other two in between.
Not surprising really as all 4 surveys and installations would have been from The Mark Group.

[The house was a set up in that WHICH? had found one with exposed damaged walls, that was at risk of allowing water into the insulation.
Surprise surprise all the "surveyors/advisors" recommended and sold the Cavity Wall Insulation to the unsuspecting punter, only two of the 8 quotes included the survey results. - caveat emptor].

ronlizpatsimon

Hello John,

My system (normally) comprises a gas fired boiler wihich sends its hot water to a storage tank in the airing cupboard. Radiators get heated from the centre part of the storage tank. That storage tank has a 3kw immersion heater fitted. This can be energised by throwing a switch in the airing cupboard. We do not have cheap electricity at night. Anyway; a timeswitch turns off the gas fired system and radiators at night. A cup of Horlicks and a good quilt is then more than sufficient

John_Pierpoint

"A gas fired boiler sends its hot water to a storage tank in the airing cupboard. Radiators get heated from the centre part of the storage tank"

I don't understand the second sentence. In an old fashioned gas central heating system, there would have been an expansion tank in the loft and two feeds taken off the boiler. One would have fed the heating coil in the hot water tank and the other would have sent the boiler water round the radiators. Having a feed that appears to do both at once is unlikely, as your would end up with warm radiators in the summer. Perhaps you have motorised valves, so that there are in fact two circuits.
Then the hot water can be given priority by the controller, when children and visitors try repeatedly to empty the hot tank?

I think it is only the efficiency of your boiler (and the strength of the sunshine and capacity of your panels) that you would need to consider before turning on the electricity rather than the gas.

ronlizpatsimon

Hello John. Your comments are very interesting.

I am not an expert on CH or plumbing but I can add a little information. Our system is, I believe, called sealed. There is no expansion tank in the loft or anywhere else. There is however a small pressurised tank mounted just above the storage tank. Normally no adjustments are needed but there is a control which can reduce or increase the pressure within this little pressurised container (useful if you lost some pressure due to a leakage perhaps).
I believe that there is only one outlet from the gas boiler and that it feeds the central part of the storage tank. This liquid is contantly being recirculated and thus can contain an anti-rust chemical. As the central core of the tank gets hot, it conducts heat to the outer part of the tank, which contains fresh water for supply to taps and showers. The general control of the radiators is by use of a single thermostat in the hallway.(thus they will not come on in Summer) Individual radiator control is also possible as each has a theremostat.
No there is no priority system. If visitors use up all the hot water in the outer part of the storage tank, it just fills with cold water, which then heats up until the tempeture reaches that which I have set on yet another thermostat (which I have not mentioned before). This thermostat is mounted right next to the storage tank

Equaliser123

Can anyone give a ballpark figure of how much solar generated electricity would have to go to the 3kw immersion heater (and topped up with grid provided electricity) to produce lower cost water heating than a gas fired boiler (rated, say, C efficiency)?