Solar Thermal or PV with EMMA?

[Richchad]

Firstly hope this is the right forum for my question, I am considering the installation, by others, for Solar roof panels.

The main roof faces South West and I have a smaller roof facing South East, I was going to install 16 PV panels on the main roof but not sure if to fit a solar thermal panel on main roof or on the South East roof for morning sun.

Or as an alternative to fit just PV panels with an EMMA to divert unused power to an immersion heater?

 

[TheMightyGusset]

An EMMA will not be cheap, and using it as you suggest I doubt if it'd ever pay for itself.
EMMAs are really only intended for larger systems

 

[Richchad]

I believe an EMMA system is about £1500 + install, but if you don't think that would pay for itself, would a Solar Thermal system at about 5k..?

Both are supposed to help heat hot water and reduce gas usage, just wondered if anyone had installed EMMA.

 

[solarfred]

We are about to install the EMMA but this is a serious PV install of 10kw feeding 3000 litre solar store. Instead of truely dumping excess production the EMMA diverts power to the water store once house demand is satisfied. Due to export restrictions we are offering the EMMA as a device that will allow 10kw as a G83. For a new build with decent loads it does make sense. Hopefully a swimming pool will really avoid any need for a dump which we are trying to avoid.

 

[Worcester]

@solarfred,

Tell me more, I've got a private 100kWP system to do (yes it is a BIG house (current house consumption 140,000kWh / annum) and we have two swimming pools to dump the excess into both heated by air source heat pumps.

 

[solarfred]

Crikey that's a project.
Our client has a newbuild and wants U/F heated by Biomass (pellet/log) with 3000 litre thermal store attached to solar thermal and PV. Export capacitiy is limited by the DNO (we have single phase) so we have been offered chance to keep the install spec by using the EMMA. Our concern is how to dump the excess production without wasting it. CoolPower have been very helpful obviously but I am concerned that we are paying for the R&D on behalf of others in the same area as the DNO is requiring some expensive options.
We have to attach thermal collectors onto a PV ground mount which has never been done before according to the suppliers plus we are using different technology to install the mounting rack rather than tons of concrete - I have spec'd ground anchors. The swimming pool option is pushing the cost up for the client but it does mean we can avoid using heaters as an easy dump. The EMMA can divert to other devices and ongoing research suggests it will be able to do more in the future. Maybe aircon which is an obvious choice when the over production is going to be Summer time. You will always need an ultimate unrestricted dump option though.Not entirely a green project but we are trying to keep it all focused as we cannot export much to the grid. We dismissed Heat pump as too inefficient.We have not installed yet as the bureacracy has to be sorted first.You will have a fair bit of spare dump capacity with two pools. Controlling it all is going to be a challenge.
If you need help with the DNO or Coolpower let me know.

 

[Worcester]

@Solarfred,

Thanks we are not worried (yet) about dumping the excess output, we'll do that as phase 2, due to the time constraints with the change in FIT. It is definately part of the overall plan though.

 

[Worcester]

@solarfred,

If you need a completely unrestricted dump, why not reverse feed ground source, have a look at this project, - he reverse feeds ground source from excess solar thermal in the summer, and then uses it in the winter:

Charging the Earth - Solar!: Introduction

In your, case, use the immersion heaters to heat the water as opposed to solar thermal and then 'supercharge' the ground, we're working on the economics vs the swimming pools because of the long-term storage option.. 'only costs 3.1p/kWh to use the electricity' still not sure if it all adds up yet though..

 

[solarfred]

We decided against Heat Pumps. The client has some acres of woods on his doorstep and is convinced he will not get fed up feeding a log boiler. (It takes pellets as well). I think the client has a lot to do with the final decision once all the options have been explored and discussed.There are some posts on another well known forum about heating the earth which may have undesirable consequences. From my own point of view if I was pumping heat into the earth what might the results be? I have no idea which is probably not a good starting point. If it heats my borehole what does the do to my water supply? We like to think we have covered some options with our plan by using three heat sources which can work in some harmony but of course the reason it may be oversized is the FIT influence. As we cannot sell the excess we have to keep the excess on site. I want to keep the house running on PV for as much time as possible and only then use it to divert to the immersion. I was not responsible for the heat pump decision but I do agree with it on current performance data. We know thermal works and we know PV works and if there is no sun we know a log boiler will work efficiently but the cost of the GSHP is less of a known quantity. The capital cost of ours will probably be a lot less then a large enough GSHP being incorporated but I have not run those number. I am keen to see if it all comes together as we predict and is totally controllable to get the best from the investment.We need to see a Winter through to see how well we did.

 

[Electron64]

Hi there

Myself and a freind have just finished this project and it works well, he has had gas almost compleatly except for a party for the last 4 months. We used a PLC and a circuit board i made to proportionally control the Immersion element as the demand of the house goes up and down. His electricity meter sits almost dead still except for a blip as kettles or stoves are put on and the system asjusts the software in the PLC.

regards
Mark

 

[echase]

Hi there

We used a PLC and a circuit board i made to proportionally control the Immersion element as the demand of the house goes up and down. His electricity meter sits almost dead still except for a blip as kettles or stoves are put on and the system asjusts the software in the PLC.

regards
Mark

There is a lot more about this sort of idea on this thread. http://www.electriciansforums.net/c...23969-immersion-heater-pv-electricity-26.html I have a similar system I designed using much less expensive components.