Solar PV getting closer but not quite there

ch750536

I try to get real world examples to work with so if you could all pull apart my assumptions on this model it would be great.

Here

In essence, investing in this would return a 30% saving on energy costs over the next 25 years based on the given assumptions.

I'd be looking for more than 40 before I'd invest. I think it will be here in a couple of years so I'll sit tight.

freddyuk

Not had a long in depth look but inflation is 4.3% average over 20 years? It may be rising quickly in the next few years where you will reduce any debt value. I estimate average energy inflation at 8% pa. and general inflation at 4% pa. You have one inflation rate?
You consider using a small proportion of generated power? If you cannot sell the power for a decent amount then you need to use as much as possible on site. Work out how you can do this and then re run the numbers. There are plenty of devices to assist this goal.
Lifestyle changes also help.

quentingargan

You show a grant of €800, but I thought that was only available on solar thermal.

But on the plus side, you can get a system like this for a lot less than €7K. Installation is quite easy.

Probably a slightly smaller system of 2kw is more optimal - you will use more of what you produce, saving the retail price of the power on a higher percentage of what is produced

It is daft that the export price paid is only 9c. That is what is really holding back the industry here. ESB buys it from you for 9c and sells it to your neighbour for twice that amount? And it is all produced at a time when electricity is in use - not at night like wind. Electricity from solar should command a higher price than wind. One day....

murphaph

quentingargan wrote: »

You show a grant of €800, but I thought that was only available on solar thermal.

But on the plus side, you can get a system like this for a lot less than €7K. Installation is quite easy.

Probably a slightly smaller system of 2kw is more optimal - you will use more of what you produce, saving the retail price of the power on a higher percentage of what is produced

It is daft that the export price paid is only 9c. That is what is really holding back the industry here. ESB buys it from you for 9c and sells it to your neighbour for twice that amount? And it is all produced at a time when electricity is in use - not at night like wind. Electricity from solar should command a higher price than wind. One day....

Yeah but in the northern hemisphere in winter it gets bright late and dark early and these dark periods are both peak energy demand periods. People are all getting up, taking showers, switching on lights, boiling kettles and then in the evening watching TV, cooking etc. Most people use more energy at home than at work too I believe.

We plan a PV + Heat Pump + Buffer Tank + UFH combo on our planned new build (in Germany). The reduction in the feed in tariff here means it also makes more sense to use the energy than sell it to the grid so it's all about how you can use energy produced at midday when you are likely not even in the house 5 days a week. I think using PV to drive a heat pump at midday to heat the buffer tank for the heating/hot water in the evening is a good way to do that. In summer we hope to use the PV to drive the heat pump in reverse mode (sort of passive AC which is available on some units). Obviously you should use timers on washing machines & dishwashers to get them to kick on during the afternoon as well, if at all possible.

In the future I hope the battery technology improves and/or the price falls to make batteries viable economically.

freddyuk

Problem is a heat pump needs a lot of PV to get it going so you will need a smaller PV and a battery/ inverter to give it the power. If you use only PV it will need to be large and you then need to use all the generation on site or get €0.09 a unit. What size heat pump are you proposing and what is the starting current?

quentingargan

murphaph wrote: »

Yeah but in the northern hemisphere in winter it gets bright late and dark early and these dark periods are both peak energy demand periods. People are all getting up, taking showers, switching on lights, boiling kettles and then in the evening watching TV, cooking etc. Most people use more energy at home than at work too I believe.

We plan a PV + Heat Pump + Buffer Tank + UFH combo on our planned new build (in Germany). The reduction in the feed in tariff here means it also makes more sense to use the energy than sell it to the grid so it's all about how you can use energy produced at midday when you are likely not even in the house 5 days a week. I think using PV to drive a heat pump at midday to heat the buffer tank for the heating/hot water in the evening is a good way to do that. In summer we hope to use the PV to drive the heat pump in reverse mode (sort of passive AC which is available on some units). Obviously you should use timers on washing machines & dishwashers to get them to kick on during the afternoon as well, if at all possible.

In the future I hope the battery technology improves and/or the price falls to make batteries viable economically.

Yes - Germany also has substantial supports for self-consumption because there is now so much solar there that it is causing supply gluts. We have the same with wind during the night. Demand side management is the best way to control this. Problem with what you propose for Germany is that there is a mismatch between demand for the heat pump (winter) and PV output (summer). In fact, in Ireland it would be ethically more valuable to export the PV electricity during the day, and run your heat pump off-peak at night (especially winter windy nights). But the tariffs don't support that.

Even using a washing machine, the load is either 2kw while heating the water, or almost nothing, so if your solar array is producing 1.5kw you are importing for about twenty minutes then exporting for the other hour that the wash is doing its rinsing and spinning.

murphaph

freddyuk wrote: »

Problem is a heat pump needs a lot of PV to get it going so you will need a smaller PV and a battery/ inverter to give it the power. If you use only PV it will need to be large and you then need to use all the generation on site or get €0.09 a unit. What size heat pump are you proposing and what is the starting current?

Honestly I'm at the early planing stages so can't say BUT the HP won't need to be very large as the house will be extremely well insulated (about 100% more energy efficient than the German 2009 building regs require) and airtight and it won't be a huge yoke, around 200m² total living space.

We're likely going to cover a whole roof slope in panels, ca, 100m² surface area. Our site means the roof will face due south. It doesn't get better for PV where we are. Our preferred house builder offers packages including a smart Heat Pump (geothermal is what we want) that can come on after other demand has been met and heat the floor/buffer tank. I think the idea of the buffer tank is to prevent the HP from cycling and just stay on until the buffer tank is hot.

If the PV is insufficient to start the HP, surely you'd just draw grid energy for a few moments until it was running and then it would be PV? Or am I misunderstanding you?

At the end of the day you have to make a call. In Germany I think energy costs are going to keep flying up and I want to have the ability to move away from grid power. PV is the start. I think turbines will get cheaper and I could see myself adding one to the roof of the house in a few years. PV is our starting point really.

ch750536

freddyuk wrote: »

I estimate average energy inflation at 8% pa. and general inflation at 4% pa. You have one inflation rate?

Got that from a good source, is the forecast rate till 2020.

freddyuk wrote: »

You consider using a small proportion of generated power? If you cannot sell the power for a decent amount then you need to use as much as possible on site. Work out how you can do this and then re run the numbers.

Yes, most power will be generated in the summer during daylight. Most power will be used during winter and in the dark hours. For this reason I believe most power will be sold at 9c rather than consumed.
Changing lifestyle is difficult. On one hand we will all go to work \ school at the same time, go outdoors when sunny. On the other we only need lights when it is dark and put heating on at night-time.

Thanks for the help, these are the things that have to be considered.

ch750536

quentingargan wrote: »

You show a grant of €800, but I thought that was only available on solar thermal.

But on the plus side, you can get a system like this for a lot less than €7K. Installation is quite easy.

Probably a slightly smaller system of 2kw is more optimal - you will use more of what you produce, saving the retail price of the power on a higher percentage of what is produced

It is daft that the export price paid is only 9c. That is what is really holding back the industry here. ESB buys it from you for 9c and sells it to your neighbour for twice that amount? And it is all produced at a time when electricity is in use - not at night like wind. Electricity from solar should command a higher price than wind. One day....

Made a new version, thanks for the details.
No grant, 2kw & 80% Tariff Efficiency. 25% payback over 20 years. The new sheet is named after you.

ch750536

Q. Is there a maintenance charge I should consider with solar PV?

Also, a 1c increase in export tariff equates to nearly €7000 over the 20 years.

murphaph

In Germany you generally factor in insurance. A hail storm can destroy an installation. It's inexpensive here but is really required. Not sure how that is in Ireland.

They'd wanna be some serious hailstones.

murphaph

Yes, such storms happen here too. You see cars written off by them on the news. Something like that is unlikely in Ireland and you'd expect the premium to reflect that.

freddyuk

murphaph wrote: »

Honestly I'm at the early planing stages so can't say BUT the HP won't need to be very large as the house will be extremely well insulated (about 100% more energy efficient than the German 2009 building regs require) and airtight and it won't be a huge yoke, around 200m² total living space.

We're likely going to cover a whole roof slope in panels, ca, 100m² surface area. Our site means the roof will face due south. It doesn't get better for PV where we are. Our preferred house builder offers packages including a smart Heat Pump (geothermal is what we want) that can come on after other demand has been met and heat the floor/buffer tank. I think the idea of the buffer tank is to prevent the HP from cycling and just stay on until the buffer tank is hot.

If the PV is insufficient to start the HP, surely you'd just draw grid energy for a few moments until it was running and then it would be PV? Or am I misunderstanding you?

At the end of the day you have to make a call. In Germany I think energy costs are going to keep flying up and I want to have the ability to move away from grid power. PV is the start. I think turbines will get cheaper and I could see myself adding one to the roof of the house in a few years. PV is our starting point really.

I got the impression you were going off grid as you mention batteries and going "away from grid power" so designing a system for on grid and then going off grid will require a different system.

quentingargan

ch750536 wrote: »

Made a new version, thanks for the details.
No grant, 2kw & 80% Tariff Efficiency. 25% payback over 20 years. The new sheet is named after you.

Hi - I don't see a link to the new spreadsheet. Though it is a bit late, and maybe I'm being thick.

There isn't maintenance, but the inverters only come with a 10 year warranty. I would sort of allow for them to need replacing once over the life of the system.

Personally I wouldn't worry about insurance. A single panel is about €150 and on a bungalow, that would be easy to fit. More problematic if the roof is difficult to access.

Capt'n Midnight

freddyuk wrote: »

Not had a long in depth look but inflation is 4.3% average over 20 years? It may be rising quickly in the next few years where you will reduce any debt value. I estimate average energy inflation at 8% pa. and general inflation at 4% pa. You have one inflation rate?
You consider using a small proportion of generated power? If you cannot sell the power for a decent amount then you need to use as much as possible on site. Work out how you can do this and then re run the numbers. There are plenty of devices to assist this goal.
Lifestyle changes also help.

Don't forget that solar PV has fallen 7% a year for at least 30 years and that trend has accelerated recently to the extent that the panels themselves may not always be the main cost.

and there are plenty of innovations in the pipeline that should reduce cost not to mention the economies of scale as output increases dramatically year after year

the pay back time is getting shorter too, the big question is when to jump,

ch750536

quentingargan wrote: »

Hi - I don't see a link to the new spreadsheet. Though it is a bit late, and maybe I'm being thick.

Original Link -Tabs at the bottom.