So now I have a solar PV system how do I make the most of it???

Doc_N

Thanks, Zeupater. Much as I thought, then. Only worse! There's no charge to me for the proposed new smart meter, but I think I'll give it a miss.

thermomonkey

Thank you for the replies, much appreciated. The solution I was looking for was, I hoped, something simple like an electric version of a fan heat transfer stove (i can't post a link).

However I may need to re educate myself on how my boiler and heating system work!

orrery

ourcornercottage wrote: »

Hi all, I'm having 3.75kw system installed in 2 weeks. I have also arranged an iSolar to attach to my current tank.

Just a couple of comments to what has been said already:
- if you are using 'variable' power from the iSolar (I don't know this device) then the heater you chose must be dumb (i.e. no timers or fancy electronics, but a standard 'clicky' thermostat is OK)
- make sure that the immersion is fitted at the bottom of the tank, as a top mounted one will give heating primarily at the top

orrery

Doc_N wrote: »

e.on are offering to fit a smart meter. They tell me that it won't enable me to gain any information at all about the solar panel output - which surprises me.

Mine tells me what I've exported, but this is of no practical use other than to warn me that I'm throwing money away. There are real disadvantages - having had mine fitted the supplier now can't switch me to E7 because they don't know how.

ChrisJD

Doc_N wrote: »

e.on are offering to fit a smart meter. They tell me that it won't enable me to gain any information at all about the solar panel output - which surprises me.

I can see clear benefits for energy suppliers, but nothing much for me. Am I missing something? Are they right in saying that these meters provide no information about output from the panels?

The official "smart meters", which the plan says are to be rolled out nationwide, are running late, and I think the final technical details are still being debated.

What you can get now is a meter which is smarter, but may need replacement when the final specification is agreed (if ever).

The meter should be able to support a remote display and thus be able to show, in real time, your consumption, and whether you are importing or exporting overall. It won't be able to separate out the PV contribution.

A possible downside is that, whereas you are normally deemed to have exported 50% of what you generate, they would be able to measure it, and only pay for what you actually exported, which could very easily be less. It would be up to them to decide.

Dave_Fowler

zeupater wrote: »

Hi

Depending on your equipment's external control features and how you envisage the control mechanism working it's certainly possible with some basic relay switching ... some inverters have the ability to control external loads so you could probably use that functionality switching in series with something similar to a certain member's immersion control circuitry would do the job as long as the heat-pump has an external demand switch interface (maybe DF will comment) ... alternatively you're looking at spending on a home automation setup ...

HTH
Z

Quite a few additions have been made to the Dave Fowler designed electronics circuitry over the past year.

To fill in the background to the project; it all started from the wish to modify a simple Owl monitor to measure either import or export.

The original simple circuit, built on a piece of 'strip' board checked the phase of the current detected by the Owl clamp-on current detector and compared it with the phase of the mains voltage. It switched the output of the current clamp to one of two outputs (import or export). I had a spare Owl meter so I was able to connect both meters at the same time. One measured and displayed import power and the other export.

The circuit which switched between the two outputs also lit an LED lamp whenever there was export current.

The second development of the circuit used the signal that lit the LED lamp to drive an off-the-shelf proportional power controller which is used to feed the immersion heater. The circuit is designed so that the control drive to the proportional controller increases slowly (over about 4 seconds) until there is less than 30 Watts being exported. At this point the light goes out and the drive to the proportional controller is decreased until the LED light comes on again at about 60 Watts export. Hence the proportional controller feeds as much power as possible (ignoring the 30 Watts offset) to the immersion heater and the LED light flashes on and off every second or so.

The next stage involved a bit of plumbing. My immersion heater is at the top of the tank and heats the top half. The pipe from the top of the tank which feeds the hot water out to the taps also has the expansion pipe to the header tank. Next to this pipe is the cold water feed from the header to the bottom of the hot water cylinder. I put a Tee junction in both of these pipes and fitted a pump (in line with a non-return valve) so that it could pump water from the hot water outlet pipe back into the bottom of the tank. The pump is connected so that it turns on whenever the immersion heater thermostat turns off. In this way the water in the hot water cylinder is stirred up. It takes about 5 minutes of pumping before the immersion 'stat turns on again and the pump stops. This occurs about four or five times before the whole tank is at the same temperature and the immersion thermostat remains off.

I've set the immersion thermostat to be at higher temperature than the tank 'stat used by the central heating boiler. This comes on in the evening if the tank has not been heated fully by the pv.

The latest electronics development enables me to use any spare power whenever there is excess above that used by the immersion heater - either when the immersion heater 'stat has turned off or when I'm generating more than 3kW. (I've a 6 kWp pv system). The circuit detects the LED 'export' light. If it has been on for more than 5 seconds, an SSR (Solid State Relay) is turned on. This can be used to send power to a heater or any other device. As soon as the LED lamp goes out for two seconds, the drive to the SSR is removed and the power is switched off.

I've put some of the design information on my website, but when the forum Mods decided I could not put a link to my site on the forum, I have not kept the website up to date. Anyone interested in further information can PM me and I'll be happy to help in any way I can.

Dave F

Doc_N

ChrisJD wrote: »

A possible downside is that, whereas you are normally deemed to have exported 50% of what you generate, they would be able to measure it, and only pay for what you actually exported, which could very easily be less. It would be up to them to decide.

Thanks for that - and the last point is particularly valid, I think, for me. We've had the panels for 4 1/2 years now, and I've devised various ways (crude but effective) of using as much of the electricity generated as possible. I'd be disappointed if I weren't using considerably more than 50% of what's generated, so a 'smart' meter would probably end up costing me money for very little practical gain.

orrery

ChrisJD wrote: »

A possible downside is that, whereas you are normally deemed to have exported 50% of what you generate, they would be able to measure it, and only pay for what you actually exported, which could very easily be less. It would be up to them to decide.

Would it, or would this remain as is? The contract terms seem unclear, but it does say that the export meter opening readings must be registered on the FIT register and I'd doubt that mine has. As far as I can see, this remains a 'theoretical' risk only.

I can't see anyone wanting to change it - they might just find that I export more than they pay me for :rotfl:

old_grouser

orrery wrote: »

Would it, or would this remain as is?
I can't see anyone wanting to change it - they might just find that I export more than they pay me for :rotfl:

Orrery,
If you have a Solarimmersion, and it's properly set up, you should be exporting very little! I export almost nothing in the summer, when the sun produces most of my hot water via the Solarimmersion box.

Dave_Fowler

old_grouser wrote: »

Orrery,
If you have a Solarimmersion, and it's properly set up, you should be exporting very little! I export almost nothing in the summer, when the sun produces most of my hot water via the Solarimmersion box.

A lot depends on the size of the hot water tank and the kWp of the solar panels. With my 'normal' domestic tank I find that around 12kWh is sufficient to heat the tank to its hottest temperature. Even one of my 3kWp systems can produce far more than this during the best summer months. Unfortunately during the summer there isn't much call for room heating, but the washing machine, dish washer and air-con can be switched on at the appropriate times now that I'm at home most days.

Dave F