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

pauldreed

Jon_Tiffany wrote: »

Provided they can keep the cost of such a unit low, it will be the must have accessory for anyone with solar pv. I would love to have such a unit, are there any guides on the web for how you built your one? Or any tips to get us started?

The difficulty is that it is not as simple as buying an electrical appliance and simply plugging it in when you get home, as the 'brain' which monitors and switches the immersion heater on and off is just part of the system.
To contruct the 'brain', you would need to be competent in soldering, and able to connect together over thirty very small components, with the experience of knowing what goes where, and which way around!
You must also have knowledge of the safety implications such as creating barriers between the low voltage and high voltage parts of the circuit. To get it wrong could prove very dangerous.

The other hurdle is that you would need a separate 240v circuit to feed the immersion heater, because it cannot simple be fed via the household primary circuit, otherwise the sensors would not work.

As I have said before, I am liaising with other people who are in the process of developing this idea to the next level, and who may market a similar device in the near future. Further development ideas include having a digital display which could display the instant/accumulated power readings, being able to notch up the power output depending on solar output, plus many others.

It is perhaps worth pointing out at this stage that I am not financially linked to this further development and do not stand to benefit in any way. I built this for me only out of interest and to utilise my solar power effectively.

Jon_Tiffany

pauldreed wrote: »

The difficulty is that it is not as simple as buying an electrical appliance and simply plugging it in when you get home, as the 'brain' which monitors and switches the immersion heater on and off is just part of the system.
To contruct the 'brain', you would need to be competent in soldering, and able to connect together over thirty very small components, with the experience of knowing what goes where, and which way around!
You must also have knowledge of the safety implications such as creating barriers between the low voltage and high voltage parts of the circuit. To get it wrong could prove very dangerous.

The other hurdle is that you would need a separate 240v circuit to feed the immersion heater, because it cannot simple be fed via the household primary circuit, otherwise the sensors would not work.

As I have said before, I am liaising with other people who are in the process of developing this idea to the next level, and who may market a similar device in the near future. Further development ideas include having a digital display which could display the instant/accumulated power readings, being able to notch up the power output depending on solar output, plus many others.

It is perhaps worth pointing out at this stage that I am not financially linked to this further development and do not stand to benefit in any way. I built this for me only out of interest and to utilise my solar power effectively.

Thanks for the extra details. I understand that its not a simple task and has all of the risks that working with mains voltage has. I guess this is why there is not currently such a device on the market. There is one exception which is the EMMA, but from memory it costs around £1k so a complete non starter for the average home solar pv system.

There is certainly a huge market for a simple (and cheap) device. Personally I would be prepared to pay up to £150 for a device. At that price range I would not be too bothered about the financial payback, I like the idea of my home becoming 'smarter' and making better use of the generated electricity.

ChrisJD

Jon_Tiffany wrote: »

There is certainly a huge market for a simple (and cheap) device. Personally I would be prepared to pay up to £150 for a device.

But wouldn't the market vanish once smart meters are rolled out, since you would then get paid only for what you export?

You might (mathematicians step forwards) be better off using E7 and running appliances at night.

ChrisJD

themaverick1953 wrote: »

Has anyone any idea how often between May-Sept a 3.96kW system would drop below 1kW output say between 0800-1200 (facing ESE)

Well, if you get dull days, it could happen quite a lot. My 3.64 kWp system is currently showing about 500 W, and spent much of yesterday below 1 kW. Nevertheless, it still generated 8.5 kWh.

When you say "how often", do you mean what proportion of the time, or on how many separate occasions?

The best you are really going to be able to find is tables such as those you can generate here. These will give you projected average daily and monthly output.

ChrisJD

pauldreed wrote: »

The difficulty is that it is not as simple as buying an electrical appliance and simply plugging it in when you get home, as the 'brain' which monitors and switches the immersion heater on and off is just part of the system.

The other hurdle is that you would need a separate 240v circuit to feed the immersion heater, because it cannot simple be fed via the household primary circuit, otherwise the sensors would not work.

And, unless you plan to have electronic power control, you may need to change your existing 3 kW immersion heater, which may then be under-powered if you have to use it conventionally. I guess the best bet would be a dual system, sometimes utilised for E7, with the lower element used for this purpose. Not a cheap retro-fit, however.

celerity

ChrisJD wrote: »

But wouldn't the market vanish once smart meters are rolled out, since you would then get paid only for what you export?

You might (mathematicians step forwards) be better off using E7 and running appliances at night.

Not really, as the export tariff is negligible - it is the FiT that is worth having.
In other words, it is financially way better to use the leccy that you generate for free, and not get any export tariff, rather than buy it in at say, 12p kWh, and sell the odd bit back for 3.1p/kWh.

Speaking for myself as an example, I would be extremely interested in a device that detected that my solar panels were generating, say, over 1000kW and then automatically switching on a battery charging pack. I could then use the energy in the battery pack to power outside lighting at night - effectively for free.

Even though I work from home with overhead LED lighting and several computers with large screens, I still only consume around 400W - so on all but the cloudiest days I am exporting far more energy than I can use (as I type this it is completely overcast and my panels are still kicking out 755W)

I could do it manually I guess in the summer, as I could pretty much assume the battery pack could be charged all day. An automated solution would be way more elegant though.

/\dam

zeupater

Hi

The real issue here is to ensure that any device which would be developed is compatible with existing automation standards. A simple device which would have a pair of clamp sensors, calculate the power differential and have a simple logic based GUI in order to control existing X10 (or other low cost automation) devices would be all that is necessary.

Utilising, and integrating with, existing technologies opens up possibilities which a dedicated device would preclude, switching in battery chargers, low power immersion heaters, fan heaters, freezers or numerous other appliances ... it would be up to the customer to be as ingenious as they wish to be in order to utilise their own power ......

HTH
Z

pauldreed

ChrisJD wrote: »

And, unless you plan to have electronic power control, you may need to change your existing 3 kW immersion heater, which may then be under-powered if you have to use it conventionally. I guess the best bet would be a dual system, sometimes utilised for E7, with the lower element used for this purpose. Not a cheap retro-fit, however.

I had to have a 1kw immersion heater made to order which cost about £60, whilst I could have got a 3kw heater off the shelf for about £20.
Fitting it was a p*g! as the blanking plug on the tank was seized up.

As you will no doubt realise, it will be a few years before I recoup my expenses, but I have got the PV system for the next 25 years or so...

As for when a smart meter is fitted, well it won't make any difference to me as I don't get paid for exported power anyway (rent a roof).

bjohnson

SMA market a device called the Sunny Backup system S which has a rechargeable battery and is mainly designed to cope with power cuts but their literature seems to say that it can be used manually to provide power at night, say. It integrates with their inverters but I've no idea what the price is.

ChrisJD

zeupater wrote: »

Utilising, and integrating with, existing technologies opens up possibilities which a dedicated device would preclude, switching in battery chargers, low power immersion heaters, fan heaters, freezers or numerous other appliances ... it would be up to the customer to be as ingenious as they wish to be in order to utilise their own power.

Eventually appliance manufacturers are expected to include facilities for working in conjunction with smart meters and new pricing schemes, which will reward those who can reduce non-vital loads on demand. There doesn't seem to be much known about these right now, but there are a host of possibilities which might be explored.