Installing Solar_cells

[peterb]

Well, after a lot of thinking and research, I have taken the plunge and had solar cells installed on my roof.

I have ben thinking about it for a while, but I've had some misgivings about the solar industry, and the reduction in feed-in tariffs has made the proposition less attractive, but there have been advances in technology and so I have gone ahead.

My roof area is limited, and faces South-East/North-West, but as a large part of the overall cost is installation, it made sense to install as much as I could, so I had 10 panels on the south-east facing side and 6 on the north-west side - each panel is 250W and so 16 gives me the maximum domestic installation size of 4KW. (Top of the picture is North west - taken in the late afternoon/evening)



One of the effects of this is that it will probably never generate maximum power, but I will generate a useful amount over a longer period of daylight hours. The technology is quite interesting - traditional 'string' arrays are connected in series and feed one inverter - this means that any shading of one panel affects the output of the whole array. This can be overcome partly by installing multiple arrays, each with its own inverter. however, my system uses one micro inverter per panel, so AC is generated at the panel, and the inverters are connected in parallel to the grid, via a generation meter. The peak power since installation was just over 3KW. One of the benefits of the system is that the inverters are all controlled from a central device so I can see statistics for each inverter as well as the whole array - current generation, and energy production - which are presented graphically.

Apart from overcoming the effects of shading, it allows each inverter to track the maximum power producing point (MPPT0) of each panel, as this varies with panel illumination, so it maximises the energy harvest. So far my array generates about 10KWh/day, although that will decrease as the nights grow longer.

So thats the technology - what about the economics?

I will be paid just over 14p/per KWh generated - regardless of what happens to it, whether it is exported or used ny me. Additionally, it assumed that half of what I generate will be exported, whether I export more or less, so I don't need an export meter. In practice it means I get paid 17p/KWh which works out as an estimated at about £620/pa.

The interesting part comes in the saving aspect on my electricity bill. As it happens, my import meter was an old one, and ran backwards when I was generating more than I was consuming. Technically that is illegal, so I told my supplier and the meter has been changed. But it did get me thinking.

Let me give an example. My general background load in the house is about 250W - mainly fridge, freezer and a server. So in 12 hours the cost would be 3KWh at 15p or 45p. So as soon as my array generates more than 250W, I am saving that per day. but it generates more than that, so I ned to use that where I can. One way is by heating my hot water with the immersion heater rather than by gas.

I now have an intelligent immersion heater controller that senses the house input current, and if I am exporting power, diverts the excess to the immersion heater (it pulse width modulates the heater supply so it matches the excess generated power. If I use something else, it reduces the power to the immersion heater to compensate)

But as an illustration:

Lets say my array is generating 1.5KW and I plug in my kettle. My kettle is a 3KW kettle, and takes 3 minutes to boil a cup of water consuming .15KWh. so it takes half the power it needs from the array (free) and half from the grid or .075KWh. If I make 6 drinks, I will pay for .3KWh. But if I had a 1.5KWh kettle, I would use my own power only, so not paying anything - but my kettle would take 6 minutes to boil. I'd still be using the same energy, but it would all be mine.

Now the cost in this example is small. .3KWh is about 5p, but over the year that adds up to £18.00! But the principle is that I need to smooth out my electricity usage throughout the day - so I shouldn't run the kettle, dishwasher, washing machine, tumble drier, cooker all at once! And this has altered the way I do things. I put appliances on serially so I have a smaller load for a longer period of time, and the same applies when I am cooking.

I also have a slow cooker (crock pot type of thing) which takes 200W, so I will be using that more frequently, and I have brought out of store an oil filled radiator connected to a second output of the immersion heater controller so when my water is hot, it provides a little bit of background heat. since the panels were installed, by gas consumption has been zero! And when I do put the gas central heating on, the power for the pump and controls should be partially met (during the day) by the panels.

Time will tell what the actual savings will be, but it is interesting to see how my attitude to energy consumption has changed.

Anyone interested in the immersion heater controller http://www.immersun.co.uk

(Oh yes, I only use my 1600W vacuum cleaner when the sun is shining! )

[Moby-Dick]

Yep - you learn to do things in a serial fashion - neat idea on the immersion control - sadly I'm on a combi boiler so its not a trick I can use. That said in the last 3 months I've only spent just over £110 on gas and electric , which is quite a significant saving!

[Zak33]

Top thread

Right.. kettle first...

Camping shops online.. low wattage... you;ll find them around 900W

slower but effective for your needs

[Zak33]

http://www.amazon.co.uk/Swiss-Stainl.../dp/B00C765DO8

like that

[Zak33]

next idea.. the low wattage hot water urn

http://www.amazon.co.uk/Igenix-Stain...ords=1000w+urn



950W... if you can get it to come on when the sun is out.. you're sorted all day long.

Fresh water every morning... job done

[Zak33]

then you can use boiling water to kill weeds on your patio... for free with no chemicals.

[Rob_B]

Dare I ask what the total cost of panels plus extras such as the immersion was? Estimated time to recover the cost is?

[jimbouk]

Did you look into the heater panels rather than the electric panels for comparison as to how they would affect your bills? I've read good things about them, but it may have just been Eco talk rather than economics.

[Noxvayl]

You make eco talk sound good when you compare it to economics jombouk

Looks really good peterb, the change in behaviour is interesting to say the least. I would like to hear what cost reduction you have achieved in a year, I suspect the second year will be better as your new routine gets refined.

[peterb]

Yep - you learn to do things in a serial fashion - neat idea on the immersion control - sadly I'm on a combi boiler so its not a trick I can use. That said in the last 3 months I've only spent just over £110 on gas and electric , which is quite a significant saving!

That's encouraging - gas is relatively cheap - my annual gas and annual electricity bills are about the same, most of the gas cost is over winter, but if I can reduce gas consumption to near zero during the sumer, that will be a plus. I do save energy on some days of the week by having my shower at the gym after a work out! (Offsets the gym membership fee!)

Top thread

Right.. kettle first...

Camping shops online.. low wattage... you;ll find them around 900W

slower but effective for your needs

Now that I do like, and I see that other people withbsolar panels use it. I am also tempted by this

http://www.amazon.co.uk/Vektra-Eco-K.../dp/B00IS3LFHI which is slighly bigger at 1.2l and 1300W, or this

http://www.amazon.co.uk/Vektra-Elect.../dp/B00IAQ9VRY at 1800W.

Its getting the balance between convenience and saving so I'm still weighing up pros and cons.

next idea.. the low wattage hot water urn

http://www.amazon.co.uk/Igenix-Stain...ords=1000w+urn



950W... if you can get it to come on when the sun is out.. you're sorted all day long.

Fresh water every morning... job done

Again a great idea, but relies on controlling the heat input in the same way as the Immersun unit which PWM the output to the immersion heater (the thermostat will be a simple on/off - ie, all or nothing). The Immersun unit will control up to thre units, but that is upstairs, so I'd have to run a separate power feed to a dedicated socket. The alternative would be a second Immersun (they can be daisy chained, wirelessly) but the Immersun units are around £350 so the payback time would be quite high. And I NEED hot water water for my first cup of tea in the morning, so if it is dark, I'd need a kettle anyway. Which is why I quite like the Vektra!

Dare I ask what the total cost of panels plus extras such as the immersion was? Estimated time to recover the cost is?

Now that is a VERY good question - but not a simple answer.

First of all, the installation cost just over £10,000. Yes, I drew a sharp intake of breath too! (And that includes AT at 5% - solar installations are rated at the lower rate if they are installed by an approved installer - which they have to be to qualify for the IT payments)

Now, looking at it as an investment - pure and simple. I estimate that I will earn £620 a year and hope to save at least £200/year on my existing energy bills. So that is an income of £820, which gives me a tax free return of 8.2% which is about as good as you'll get anywhere. And the Feed in tariff is linked to the RPI and guaranteed for 20 years, and energy prices are likely to rise, so the ROI may increase - even allowing for the reduced efficiency of the panels as they age. BUT - unlike a conventional investment, you can't sell or withdraw your cash - at least not until you sell the house, and it is then uncertain how much it enhances the house value. Now I think and hope that the savings and earning will be more than that, and the projected savings are nearer the £1,000 mark, but I won't really know what the actual figures are until next year. You could also argue that it isn't really paid for until you have got back the original investment and then start taking the profit.

It gets more complicated if you take out a loan, as I did. In that case, I need to look at the point at which I have paid off the loan and interest, and that would be between 6 and 10 years - but in practice I'l pay that off earlier. Again you could argue that it isn't really paying for itself until the loan and interest are paid off.

So in either case, it is a long term thing. Yes, if I move house it should add value and make the house more saleable, but I'm not planning on moving for a while yet. But it does take a lot of research and careful look at circumstances.

There is a large leap of faith in this - my gut instinct says it will be worth it, but it is a long term investment

Did you look into the heater panels rather than the electric panels for comparison as to how they would affect your bills? I've read good things about them, but it may have just been Eco talk rather than economics.

I looked at it, but in the UK it is rare that solar thermal will get hot enough to heat domestic hot water (DHW) to an acceptable temperature on its own. It is good for pre-heating water that will then be boosted normally, but that would need a dual coil indirect hot water tank, and/or underfloor heating. Underfloor heating is not possible in my house. Installation is more complicated and requires some plumbing. Great for a new build, but not quite so good for retrofit.

I am lo0king at replacing the hot water tank with one that has a heating coil and two immersion heaters ("economy 7" tanks) so the Immersun heats the top of the tank first, then when that is up to temperature, diverts energy to the bottom one. However, that is anther £400 or so, and the payback period is still quite long.

You make eco talk sound good when you compare it to economics jombouk

Looks really good peterb, the change in behaviour is interesting to say the least. I would like to hear what cost reduction you have achieved in a year, I suspect the second year will be better as your new routine gets refined.

Yes, a year on will be interesting. There are a lot of factors involved. I have modified the use of appliances - I now turn my monitor off for example - a bit more energy going to the hot water tank! I already had my dishwasher filling off the hot water supply, so that is a bit more efficient. However, convenience is a consideration, as is the fact that I work from home quite a lot. If I was out, I'd be looking at other ways of maximising use. The slow cooker should help too.

Cooking is an interesting one. My oven is conventional electric with a simple thermostat, so when it is on - it takes 2.5KW, when off, it takes nothing. No proportional control of the heat output. So not good for using my solar energy, but does ensure the oven heats up quickly. The hob is induction, and I have to investigate how that controls energy output.

At low levels, the 'rings' seems to operate on the thermostat type principle - on for a bit, off for a bit, but at higher levels, the control seems to be proportional. So I need to try to determine what the input current is at low levels when it is on, and how that varies at the higher levels. A clip-on ammeter might be the solution.

My background load during the day (and night) is about 200 - 250w, (Mainly fridge and freezer) so taking the 200w figure that is about 5Kwh. Assuming a 50/50 split between day and night, and given that during daylight the system rarely produces less than 200w, every day I am saving 37.5p, which over a year is £135. and I think in reality it will probably be more than that as the day time quiescent load may be a higher proportion.

But it would be easy to get obsessive about this - yes, I'm looking to save money, but not to the extent when that starts impinging on the quality and convenience of life, and I'm sure I have yet to find that balance. I am reading my meters weekly at the moment so I should get some idea of the savings before my next bill which may inform the decisions about more energy saving measures - and the ROI.

[TeePee]

Now, looking at it as an investment - pure and simple. I estimate that I will earn £620 a year and hope to save at least £200/year on my existing energy bills. So that is an income of £820, which gives me a tax free return of 8.2% which is about as good as you'll get anywhere. And the Feed in tariff is linked to the RPI and guaranteed for 20 years, and energy prices are likely to rise, so the ROI may increase - even allowing for the reduced efficiency of the panels as they age. BUT - unlike a conventional investment, you can't sell or withdraw your cash - at least not until you sell the house, and it is then uncertain how much it enhances the house value. Now I think and hope that the savings and earning will be more than that, and the projected savings are nearer the £1,000 mark, but I won't really know what the actual figures are until next year. You could also argue that it isn't really paid for until you have got back the original investment and then start taking the profit.

I struggle to see this as a good investment. An 8% return is about what you would expect from the stock market over a long period of time, after adjusting for inflation. If energy price rises match inflation, then with an investment in the market you'd have the benefit of keeping your initial investment and, more importantly, compound interest. $10K invested in the market ten years ago would be worth over $22K today. You are looking at ten years just to pay back an investment that may or may not hold any value in ten years time, depending on, among other things, the solar panel industry. With technological developments, solar panels will only decrease in price and increase in yield. I can't foresee ten yea old panels adding substantially to the value of a home. To beat the historical market, you'll need the average price of electricity over ten years to be three times your current electricity price.

From a technology perspective, fantastic set up!

[badass]

Any idea what happens when there is a power cut?
A little birdie told me that when there's a power cut, you don't get the power of the panels. I.e. you don;t get a daytime UPS for low loads.
My initial thoughts were that's untrue but then thinking about how such a setup would handle more load than it can generate and I'm not so sure now.
I've been considering this myself but as I am planning on an extension that will have a substantial effect on the roof in the next 5 years I've decided to not bother looking into it further.

On the economics side, if you've got a loan out and assuming you've contributed nothing, it's paying out every month that the savings outstrip your repayments. Anyone that suggests the payback is anything other than instant in that situation is missing the point. However you are performing a "leveraged" investment.
Of course, this doesn't apply in the same way if you have a shorter term loan than say 11 years.

[peterb]

I struggle to see this as a good investment. An 8% return is about what you would expect from the stock market over a long period of time, after adjusting for inflation. If energy price rises match inflation, then with an investment in the market you'd have the benefit of keeping your initial investment and, more importantly, compound interest. $10K invested in the market ten years ago would be worth over $22K today. You are looking at ten years just to pay back an investment that may or may not hold any value in ten years time, depending on, among other things, the solar panel industry. With technological developments, solar panels will only decrease in price and increase in yield. I can't foresee ten yea old panels adding substantially to the value of a home. To beat the historical market, you'll need the average price of electricity over ten years to be three times your current electricity price.

From a technology perspective, fantastic set up!

Well any investment carries a risk, generally the higher the risk, the higher the return, and a stock market investment is subject to dealing costs, capital gains and income tax - and the short term market movements. Investments in any house improvements is also perhaps questionable. I could have 'invested' in improved insulation - probably in the form of upgrading the double glazing, which would reduce energy consumption, but again difficult to quantify in terms of 'added value' to the house.

The solar cells are generating income, and reducing my on-grid energy consumption. You could argue that the income from (say) a fixed interest bond could be used to offset energy consumption payments, and that becomes a partly philosophical argument! From a practical point of view, the energy that was going to waste heating my roof and then the atmosphere is now being used to reduce my energy costs - before ultimately ending up heating the atmosphere! In terms of total energy consumption, that may reduce slightly, but the aim of the game is smoothing out the load so I use more of my solar generated energy and use les paid for energy from the grid. And that feed in tariff that is linked to the cost of living index is guaranteed for 20 years, so if I did sell the house in ten years, a selling point is the residual value of that FIT. But as with most investments, there are a lot of 'what ifs'!

Any idea what happens when there is a power cut?
A little birdie told me that when there's a power cut, you don't get the power of the panels. I.e. you don;t get a daytime UPS for low loads.
My initial thoughts were that's untrue but then thinking about how such a setup would handle more load than it can generate and I'm not so sure now.
I've been considering this myself but as I am planning on an extension that will have a substantial effect on the roof in the next 5 years I've decided to not bother looking into it further.

On the economics side, if you've got a loan out and assuming you've contributed nothing, it's paying out every month that the savings outstrip your repayments. Anyone that suggests the payback is anything other than instant in that situation is missing the point. However you are performing a "leveraged" investment.
Of course, this doesn't apply in the same way if you have a shorter term loan than say 11 years.

No, it is a regulatory requirement that on-grid systems shut down if the grid power is cut off. Apart from anything else it is a safety issue, you really don't want to be feeding power back into the grid if there are people working on what they thought was a dead circuit. And that is true of any micro-generation system that feds power to the grid. There are off grid systems that are independent (and you still get the generation payments, but not the deed in portion - provided it is installed by an approved installer). There is also a re-synchronisation issue when power is resupplied - synchronising lots of small generators with the grid is easy for the small systems. Synchronising the grid to lots of small uncontrolled small generators is less easy and is likely to damage the small systems!

On the economics side, yes, it is leveraged. I was initially offered a ten year loan (with early repayment options that would reduced the total interest) but I found a better deal for a 5 year loan. So initially my capital plus interest payments will exceed my income and savings (but I have a mechanism that will repay the loan early anyway) so the viability and actual return on investment is very much down to individual circumstances.

If you are planning a house extension, you might want to think about underfloor electric heating if solar_PV is still of interest to you. Underfloor heating linked to something like the Immersun is a good heatsink for surplus energy.

As I said earlier, there is an element of faith in this, but I am getting paid for what I produce, and I will reduce my energy costs so in the long term, it will pay for itself and then generate income.

[Butuz]

Coolio! IME you'd have been better having them all installed on the south east side to maximise ROI.

Be interesting if you keep this thread updated with your monthly generation and reduction in bills?

Butuz

[peterb]

Coolio! IME you'd have been better having them all installed on the south east side to maximise ROI.

Be interesting if you keep this thread updated with your monthly generation and reduction in bills?

Butuz

The roof isn't big enough to have all the panels on one side, but while the peak power production may be less, power is produced over a longer period of time as the panels on the NW face generate later.

I will keep the thread updated!

[Zak33]

nice photos of the panels in situ by the way