Solar water heating and combi boilers

[Colin Wilson]

Some suppliers support export arrangements, but not many at present - I believe this is something being taken up at regulatory level with the government in line with the proposals for "green" energy targets.

The backfeed issue is, as I am lead to believe, mute, (i`ve raised the question myself) as any connected load on the network will dissipate the export rendering it effectively safe (and anyone working on the network should be treating it as live regardless) - but the protection should really prevent export in the event of the loss of mains supply.

The energy minister a couple of years ago (a scottish bloke IIRC) was touted as the first "user" of a turbine generation device that was described as simply plugging into a standard 13A socket - I got little mental alarm bells ringing back then about export / protection !

Whether multiple backfeeds may cause a problem in the event of the failure of one isolating protection device on a segment of network, thereby putting a voltage back onto the network that may fool other isolating protection devices to think the mains are energised on the other hand... Even better if it happens to backfeed something like a pole mounted transformer - which, lets face it, is likely to be common in sites with wind turbines as they`re often remote.

Other issues you will likely encounter are:

• Standard supply / connection agreements do not typically allow for export.

• Metering of the installation / export - the metering is relatively costly compared to a standard meter (possibly due to low volumes).

• Electronic meters may flag up illegal abstraction if the supply happens to flow in the "wrong" direction.

• The local meter operator may not be in a position to fit the metering specified by the supplier - in which case the supplier may need to send a meter fixer a considerable number of miles to do it for them - thats assuming the local REC allow export back to the network in the first place...

A suggested work-around I heard was to give anyone exporting an "allowance" off the bill, but how that would be policed is anyones guess

- everyone will say they`re generating to knock a few quid off ! (and if the customers' generation equipment fails, how would this be detected to allow the bills to be adjusted)

For exporting less than 16A/phase I believe G83/1 applies, otherwise look at G59/1

[David Hansen]

On Tue, 23 May 2006 22:13:43 GMT someone who may be John Stumbles wrote this:-

Much the same as connecting a small wind turbine I presume. With these it must not output electricity if there is not an external voltage from the mains.

There are essentially three parts. Firstly reductions in importing electricity. Secondly payment for exported electricity. Thirdly amalgamation by your supplier of renewable certificates. As an example

is one offer.

[Mary Fisher]

What happened to that system?

Mary

[David Hansen]

On Wed, 24 May 2006 10:54:16 +0100 someone who may be "Mary Fisher" wrote this:-

It was probably the windsave

course the "plug-in" idea is to some extent a marketing gimmick. I certainly wouldn't have one in any property I look after. However, as they say in

"How safe is the system if the plug is pulled out of the socket?

"There are two aspects here to be aware of. Please note that the applicable regulations demand that our system is safe in all modes of use, or indeed, 'non-use'. We typically hard wire into a fused spur, so there is no inadvertent disconnection available in normal use. When we do use a 'plug in ' technique , the socket for the 13A plug is also made safe from 'inadvertent unplugging' by means of a safety cover, which requires a tool (and a 'responsible person') to remove it. However, also please note that the standards do also require the system to go 'dead and safe' within 0.4 seconds maximum. We comply with this, but the above two methods also work to preclude this aspect of any part 'exposed' remaining live for personal contact."

[Colin Wilson]

Not a clue, I never got any answers...

[Mary Fisher]

I don't understand any of that - but is the company still going?

Mary

[David Hansen]

On Wed, 24 May 2006 20:11:04 +0100 someone who may be "Mary Fisher" wrote this:-

They only use the plug approach if they have to. Normally they wire it into a suitable connection unit, of which there is an example at

they have to use the plug approach then the plug is fitted with a cover that is screwed into the socket, so that it cannot be accidentally withdrawn.

No matter how it is connected, the controls are arranged so that if the external mains voltage disappears then within 0.4 of a second the controller will stop outputting power to the mains wiring. I assume it also brakes the wind turbine to a standstill. The external mains voltage could disappear because the plug is withdrawn, the cables are removed from the connection unit or cut, or the external supply fails (a power cut).

This does mean that in a power cut the turbine cannot supply electricity. There are ways round this, but these are best supervised by a suitably qualified electrical engineer.

As far as I know. The second wind turbine put up on the BBC2 television programme 'It's Not Easy Being Green'

was one of theirs.

[Mary Fisher]

electricity how can it be used by putting it into the domestic wiring which is designed to deliver power, not accept it?

...

I've saved that to peruse later. Some things look interesting but I haven't time now, off to Scotland tomorrow. Back next week.

Don't go away ... :-)

Mary

[John Rumm]

The simple answer is, the domestic wiring does not care... much the same way you can have two batteries in a circuit and draw powwer from them both.

[David Hansen]

On Thu, 25 May 2006 22:30:58 +0100 someone who may be "Mary Fisher" wrote this:-

In essence what it does is reduce the amount of electricity drawn from the external supply. If the house is not consuming as much as is being generated then the surplus is fed into the external supply by the control system.

In the water analogy, water can be sent either way along a set of pipes with branches. In electricity the "water" is not actually flowing in one direction. Rather it is flowing in one direction and then the other constantly. Thus there is no great problem accepting the wind generated electricity in current circumstances. In fact local generation tends to smooth operation of the local system.

There would be more serious problems if a large proportion of electricity was generated in this way.

[John Rumm]

Talking of which, you still have not told us what water softening you use with your solartwin system.

[Mary Fisher]

I'm sorry, I don't remember seeing the question. We've been very busy and have had lots of distractions ...

We're not using any water softener, why should we?

Mary

[Mary Fisher]

Well, I know I'm only a simple little grey haired old woman but if I tried to put water from our rain butt into a domestic water tap I'd be surprised if it would be acepted.

Now you can show off your physics - but not in words of one syllable, please, I do have a smidgeon of the old fashioned variety.

Mary

[Mary Fisher]

Ah - so there's some system to 'control' it ... it doesn't just go through from the generator into the power outlet.

Alternating current I understand.

I understand that, thank you.

But I hadn't heard mention of an intermediary control system.

Mary

[Steve Firth]

Seconded. You forgot to add that you;re a simple grey haired old woman who believes in an imaginary friend.

If it were of the same quality as tap water then it's feasible.

Does your rain butt have a filter and chlorination equipment? A domestic generator suitable for on-line use is supplied with equipment to match the voltage and phase of the generator to the mains, which means that subject to an agreement with your supplier and suitable metering equipment it's permitted to generate your own electricity and supply it to the grid.

[PeTe33]

Think of voltage as "pressure" or in the case of water then "bar"

If your water butt was full and was 30m tall you'd have 3 bar of pressure at the bottom of your butt. :¬)

If you then plumbed it in to your domestic water pipe which has a pressure of 2.5 bar then the water from your butt would indeed flow into your pipes until the butt had drained down by 5m to give the same effective pressure as your water supply (i.e. the level/depth of water in your butt is 25 metres from bottom to top.

With me so far...

At which point, when you turn on a tap in the house water would flow equally from the water but to the tap and from the water main to the tap. EXCEPT.... the water butt would be a reducing water pressure as the level reduced whereas the water supply from the main would be pretty constant. in other words, the water butt would now be acting as a "pressure storage" device. All water would flow from the water main to the tap UNLESS the water main pressure dropped, at which point water from the butt would now flow into the house until both pressures are again equal.

In the mean time.... it's raining.... an awfull lot, and isn't stopping. your butt is now trying to fill up, but as we know,when it is full it has 3 bar of pressure. so........ all the time it's raining and your butt is trying to create more than 2.5 bar of pressure, the excess water (that which would take the water deeper than 25m is overcoming the pressure in the water main and water is flowing into your house to cover any demand made from open taps etc.

Where there is no demand, the water from the butt keeps trying to equalise the pressure between the water main and it's self, and flows back out of the house along the pipe to the water meter, through the water meter and into the big pipe in the road.

This action causes your water meter to actually run backwards as you are returning water back to the system.

Conclusion.

Volts (electricity pressure) = Bar (water pressure) Wind = Rain

If volts or bar are equal from 2 sources (water main & water butt OR electricity supply & wind turbine) in the same circuit power will be used equally from both sources. If volts/bar from one source is greater than the other then the source with the biggest numbers will be the supplier of the energy/water.

Only thing that doesn't quite tie up is that there will always be 240v on the ring main and the wind turbine will never output anything above or below 240v so I can't really see that the electricity meter would ever actually run in reverse as some might suggest.

HTH

[John Rumm]

Erm, well if you have soft water already then there is no need. If you don't, then the solar system will scale up since it is continualliy being fed fresh water rather than recirculated water.

(hence the original question about whether you local H2O was already soft)

[John Rumm]

Well to use your analogy of the water butt, if you had a pump on it to raise the pressure so that it was comparable to that of your mains supply, then it would be "accepted" in the sense that when you turned on a tap you would end up with a mixture of rain water and fresh water coming out.

In the case of a power system, the "pressure" is voltage, and the "flow rate" is current. So get the pressure (voltage) right, and turn on a tap (plug in an appliance), and water (current) will flow from both sources.

You will need a few no return valves in there to make sure you don't end up back feeding your generator with mains power, and to ensure that if you do back feed the mains supply with your generator, it is only done under certain controlled conditions.

(one presumes that the local generator must also have some way of aligning the phase of its output with that of the main supply)

[David Hansen]

On Tue, 30 May 2006 22:54:19 GMT someone who may be "Pet @

;¬)" wrote this:-

230V plus a little or minus even less.

It will output a suitable voltage and waveform so that energy flows "backwards" into the electricity system. Both voltage and waveform are created electronically.

Many meters don't, because they are designed not to, but it would be amusing to have the sort that does.

[David Hansen]

On Tue, 30 May 2006 22:17:01 +0100 someone who may be "Mary Fisher" wrote this:-

The photograph at the top of

shows the box from one manufacturer. This chops up the DC from the turbine and converts it to a suitable AC to output. This is a standard process now, used in many applications, including trams/trains and the UPS systems some have their computers plugged into.