Solar PV vs Grid

[coulter]

The problem with that approach is that there will be times when you have say 200w to 4000w of excess energy but you cant run the heatpump on that so that power is lost / fed into the grid. A battery could absorb that power to be used later.

Thank you, yes I was thinking of signing up with my supplier to receive the export tariff for any excess that I don't use to start with, then see if the battery is still viable or not to be added at a later date.

 

[coulter]

The problem with that approach is that there will be times when you have say 200w to 4000w of excess energy but you cant run the heatpump on that so that power is lost / fed into the grid. A battery could absorb that power to be used later.

Some of the suppliers are now offering up to €0.14 per kwh here!

 

[johnb2713]

Some of the suppliers are now offering up to €0.14 per kwh here!

If the price is that low, I wouldnt bother with any solar / battery system.

 

[BorisJ]

Bob,
This is easy, heat the water on off peak energy (7.5p kWh)

Or your gas boiler which is cheaper still.

 

[johnb2713]

Or your gas boiler which is cheaper still.

Gas boiler isn’t cheaper, immersion on off peak power is way cheaper than gas 7.5p 100% efficient v 11.3p with 92% efficiency

 

[BorisJ]

My gas is way cheaper than that.

 

[Gian]

Gas boiler isn’t cheaper, immersion on off peak power is way cheaper than gas 7.5p 100% efficient v 11.3p with 92% efficiency

My lpg is 57p per litre it's very expensive so we have had to cut back for sure. But I am not happy having all my eggs in one basket so I will be keeping my gas boiler,infact I will be changing it out for a new one shortly with H2O ready. I do not want all my home running totally in electric as I can see huge issues coming for all homes as people switch to EVs and heat pumps. I just ordered a 10kw Genny to future proof my home ready for power cuts as everyone jumps to electric. Lots to think about being totally reliant on electric when you have a family .

 

[johnb2713]

My lpg is 57p per litre it's very expensive so we have had to cut back for sure. But I am not happy having all my eggs in one basket so I will be keeping my gas boiler,infact I will be changing it out for a new one shortly with H2O ready. I do not want all my home running totally in electric as I can see huge issues coming for all homes as people switch to EVs and heat pumps. I just ordered a 10kw Genny to future proof my home ready for power cuts as everyone jumps to electric. Lots to think about being totally reliant on electric when you have a family .

I understand totally and still have my gas boiler ready to use.

I am however expending my battery storage to 23 kWh and inverter capacity to 12kW with a 10kW generator also planned into the system. I aim to be able to run completely on batteries during peak periods and then charge the batteries off peak / by solar / or by generator as required.

 

[Bob Smith]

I understand totally and still have my gas boiler ready to use.

I am however expending my battery storage to 23 kWh and inverter capacity to 12kW with a 10kW generator also planned into the system. I aim to be able to run completely on batteries during peak periods and then charge the batteries off peak / by solar / or by generator as required.

Hi John
what type of 10kW generator are you talking about?

 

[johnb2713]

I

Hi John
what type of 10kW generator are you talking about?

'm looking at two, one of them is a Hyundai in an acoustic enclosure with a belly tank, the other is a bit of a homebrew one using a twin cylinder petrol engine running on natural gas driving an alternator with home design / built controller looking after it all. I would only run the generator during daytime and it should only be necessary on rare occasions for a short time.

 

[Bob Smith]

I
'm looking at two, one of them is a Hyundai in an acoustic enclosure with a belly tank, the other is a bit of a homebrew one using a twin cylinder petrol engine running on natural gas driving an alternator with home design / built controller looking after it all. I would only run the generator during daytime and it should only be necessary on rare occasions for a short time.

OK. If I understand you are trying to become 100% independent from the grid? If so, once you know your system works as per your expectation, will you expect to disconnect your house from the grid?

 

[johnb2713]

OK. If I understand you are trying to become 100% independent from the grid? If so, once you know your system works as per your expectation, will you expect to disconnect your house from the grid?

No, not quite, I will be using loads of power off peak to charge batteries and hopefully harvest some solar energy. If the off peak r=ate becomes expensive then I will go off grid and run the generator as a combined heat and power plant.

 

[Bob Smith]

No, not quite, I will be using loads of power off peak to charge batteries and hopefully harvest some solar energy. If the off peak r=ate becomes expensive then I will go off grid and run the generator as a combined heat and power plant.

Sounds an interesting project. However, you will pay for a generator that may be hardly used?

Up till beginning of this year. I thought I could charge batteries (a LOT over summer) and keep the electricity for Winter. Unfortunately, as I understand they are not designed to store the energy that long and trying to cover all your winter needs will require 1000kWh... There is no battery systems that cover that much (without even mentioning the cost...) . So I had to change my strategy.

Do you know how much kWh cost when generated by your generator?

 

[johnb2713]

Running the generator on gas and running as a combined heat and power it can be very cost effective. Running on gas gets rid of a lot of the duties applied to fuel including red diesel which is now hard to come by. Engine efficiencies at best are only 25 to 30% so gas at 11p kWh would cost around 40p per kWh of electricity. Using the heat however, the 70% waste heat then starts to become more cost effective. By charging batteries, heating hot water and heating the house while the genny is running that will give some real energy cost savings.

Earlier in my working life I did a similar project on a much bigger scale (350 kWa Volvo Generator) it fed 12 factory units, had an Allen Bradley PLC controlling it all and was fully automatic. It collected the price of red diesel on a daily basis, had the outdoor temperature and could assess the demand of each factory unit. It then made the decision whether to run off genny or grid. There were times that it had to be a generator supply because our grid feed was too small for some of the equipment we had, if that equipment was switched on the genny started and all units switched over to generated power. Likewise, if the grid supply failed, the genny started up within 3 seconds and powered all of the units.

I really enjoyed this project and it's still in operation to this day (20 years old).

 

[Gian]

I understand totally and still have my gas boiler ready to use.

I am however expending my battery storage to 23 kWh and inverter capacity to 12kW with a 10kW generator also planned into the system. I aim to be able to run completely on batteries during peak periods and then charge the batteries off peak / by solar / or by generator as required.

This is my goal, I am going down the route of v2g ev charger and I will hopefully be using a 30kw ev car as my storage.

 

[johnb2713]

This is my goal, I am going down the route of v2g ev charger and I will hopefully be using a 30kw ev car as my storage.

I personally wouldnt go the V2G route, the equipment is expensive and the additional wear on the vehicle batteries not economic, better to have dedicated LifeP04 cells and an inverter to deal with it.
Just my 10c

 

[coulter]

Thanks Guys, but in Ireland we pay around €1.20 per litre for heating oil and €0.28 per kWh for electricity and don’t have gas in the county side!

 

[Gian]

I personally wouldnt go the V2G route, the equipment is expensive and the additional wear on the vehicle batteries not economic, better to have dedicated LifeP04 cells and an inverter to deal with it.
Just my 10c

I am pricing a v2g charger I will get back to you.

 

[johnb2713]

I am pricing a v2g charger I will get back to you.

I will be interested to hear, I have a project in mind where it would be a good fit.

 

[coulter]

Hi Folks, Ok getting back to the original idea of installing these PV panels, I think I am getting near the decision point here now at last!

My current thoughts are to install two strings of 12 x 370 watt panels, one on each side of my east/west garage roof. A total of 8.88 kw connected to a 6kw Solis inverter. I would appreciate any installation tips anyone can throw in here, see pictures attached of the actual roof and the Renusol mounting bracket that I propose to use. As these are not continual rails I was wondering what is the best way to support the DC cables running under the panels, do you guys use anything to keep the cables secure and up from the roof surface and the elements?

Also, what do you think of my proposed layout, should I leave a ladder space between rows 2 & 3 for example, to allow easier maintenance or cleaning or would that just look untidy and messy? Should I run the DC cables on the outside of the roof or drill through to the inside, between the separate banks of panels?

Many Thanks.