Realistic claims for solar pv

[Brian Gaff]

2KW over how much of the hours in a year on average, its not a lot is it?

Brian

[Brian Gaff]

A friend has those water panels on her roof and has told me it saves a lot of money on bills for heating water. I guess its lower tech though and lets face it many like the idea of gadgetry!

Brian

[Andy Burns]

Is there anything wrong with maximising output?

[Tim Lamb]

:-) 500m from the nearest highway. Trees grow along river banks so the panel would probably go on the top of a 12 or 18ft. scaffold pole. The battery/controller could be in a padlocked cabinet. I suppose some sort of time delay would be required as a float over pressure switch would reset as soon as the water had fed back through the pump. Non return valve?

I suppose we need to consider pump motor efficiency.

This is likely to be an annual requirement and the cost spread over several years. It might be better to find a commercially available kit.

Hmm.. they could drink from the river if the general public had the integrity to keep themselves and their dogs on the footpath.

Thanks

>

[Jethro_uk]

That's if you are obsessed about PV solar (which conveniently is also the only solar you can sell to the grid).

Now if it was a case about being *serious* about solar, rather than a greenwashed ponzi scheme, you'd be using solar panels to directly heat water and then keep that stored in your hot tank for used whenever - thus reducing your gas/electric consumption.

[Jethro_uk]

Depends what sort. PV, yes. But even on a cold cloudy day, I managed to get water at 50+C from a 30m black hose we used along the outside of the workshop.

[Jethro_uk]

I think it's quite high tech, if you are using the vacuum tubey things :)

My primary concerns are about getting what must be quite a weight of water onto the roof, and the potential for burst pipes. Although I guess if your roof is doing it's job, a leaky setup should be no worry.

[Tim Lamb]

May to October only luckily. Last I heard, he has not yet bought the cattle!

Looking at physical size... roughly 1.6x1.0m bit big to wave about on a single scaffold pole.

Thanks for the maths!

[Pancho]

The point is in the UK we use most energy in the winter.

So yes piping hot water in the summer. I don't know about you but I spend very little on hot water.

Solar power is an excellent idea, but not in the UK.

The point I find irritating is that I'm not seeing sensible energy policy from anyone important.

A bit like Brexit, politicians would rather twiddle their thumbs than make a good long term decision that would cause problems for them in the short term.

[Steve Walker]

There's not much weight - at least with the systems that I looked into. The tubes contain little water and there is a separate insulated tank, which can be inside.

A small pump pushes water from the bottom of the tank, into the bottom of the collectors and it returns to the tank from the top. The small volume, low flow, lets the water get very hot before returning. The pump flow can be automatically varied to give slower flow when there is less sunlight and so maintain a high return temperature.

When there is insufficient sunlight, the pump stops and the water drains back down to the tank (preventing freezing in the tubes). The pump can also be stopped if the tank is getting too hot to prevent boiling in the tubes.

I looked into buying the bits separately and making my own control system. I did come up with a simple control circuit and software design when I was looking into it, but I don't think I kept it when I didn't take things any further.

SteveW

[Robin]

An urban dweller asks...

If the PV is within the field might the cows decide to test its support as a scratching post?

[Dave Plowman (News)]

There would be if it is wasted?

[John Rumm]

If you only need summer, then a quarter sized panel would likely do it based on those figures.

[Jethro_uk]

On topic: check. Useful info: check. No personal abuse: check. Adds to discussion: check.

You really need to work at this newsgroup thing, mate. It may not be for you. :)

[John Rumm]

A notional 2kW is probably something like 8 full sized panels. Seems a bit excessive for a water trough.

[Jethro_uk]

Used to. I'd be curious how much air con has changed that. (Plus the sales of gas for patio heaters ....)

To be fair, it's not a breakdown I've considered ...

Not as things stand anyway ...

I agree furiously !

[John Rumm]

Which basically means that all solar farms produce 80% (at best) of their installed capacity from gas, and wind farms at least 50%. So if you want "zero" net carbon, then neither is much use unless you can find a way of storing 7TWh of energy!

[John Rumm]

Even if you use 100L every day of the year, that usually only works out at under £150/year in gas... That kind of throws many of these multi thousand pound schemes for solar hot water into context.

[Martin Brown]

More or less guaranteed - that and trying to push it over. At least there is nothing tempting and green about it for them to try and eat!

But they will try to eat any kind of loose cable they can see too.

They like scratching themselves on my fence for similar reasons.

[John Rumm]

Even true tory's can understand basic economics... subsidy can be worthwhile when it promotes a behaviour that contributes to a common good. Much like taxation can be be use to fold the costs of externalities back into any practice where they are currently avoided. That forces the true cost of an activity back onto those responsible for it, and restores more realistic market forces.

Those that promote subsidy of renewable energy generation will argue that its an industry that is new and hence needs support to reach maturity (an argument wearing thin IMHO), and that there is a common good being achieved from the production of low carbon energy.

There are major flaws in the argument that stem from the fact that we currently have no practical use for intermittent energy sources. Hence the delivery of it must be forced to become a continuous. Either the producer of the energy must provide their own storage, or they rely on existing flexible generation capacity elsewhere in the grid to make up the shortfalls. Currently a massive externality the producer is not having to meet. To add insult to injury, most of that flexible generation capacity will be gas powered. So currently, by having grid connected solar, you just lock in a requirement for gas generation which seems to go against much of its whole stated purpose.