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Solar panels, worth the money ????
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09-09-2010 10:44pm#1
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This is the problem, and is why cold water only inlets on these machines make sense. I have to give you credit Quentin for the measures you take to ensure you use solar heated water to do your washing, but realistically they are impractical for most people, and they would also directly conflict with the possible use of a delayed start option to do washing on night rate electricity.
The much more sensible option is to manage down hot water use, for example with the newer detergents which work at temperatures down to 15C, rather than going to heroic lengths to maximise the proportion of solar heated water used.
Well for a start, 15 deg water may well wash the (white) collar workers bib's (
), but it won't shift anything I come across ! 
And you do have to wonder about the chemicals involved, to make it work at that temp......
Anyhoo - the dead leg problem isn't insurmountable - hotels and hospitals do it, using a loop system. Not advocating that in your house, but I'm suggesting that that technology on a miniature scale, even using v.small bore circuit, in the machine, would sort that. It's not rocket science. If your fridge can email you to tell you you're out of milk, I don't see why not.........:)Ode To The Motorist
“And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road”
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Well for a start, 15 deg water may well wash the (white) collar workers bib's (), but it won't shift anything I come across ! And you do have to wonder about the chemicals involved, to make it work at that temp......
Anyhoo - the dead leg problem isn't insurmountable - hotels and hospitals do it, using a loop system. Not advocating that in your house, but I'm suggesting that that technology on a miniature scale, even using v.small bore circuit, in the machine, would sort that. It's not rocket science. If your fridge can email you to tell you you're out of milk, I don't see why not.........:)
Horses for courses, as ever - personally, my washing machine only goes as low as 30C and at that I notice no difference whatever from the results of washing at 40C. Some stuff does need a hot wash of course, but the general point stands - concentrating more on reducing energy use rather than trying to switch wasteful use of energy to renewable sources is the best way to go.
As for the fridge, when Tesco can e-mail me back the milk, I'll be interested . . .0 -
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Here's my humble opinion. We live in a 3 bed semi. We have a new condensing boiler and a 190l stainless steel cylinder with a dual coil ( suitable for solar panels ). We currently heat our hot water using the gas boiler. During the Summer, when the heating wasn't being used I monitored the gas usage to estimate the annual cost of heating the hot water. This figure came out at approximately 300 euro.
A solar water heating system typically provides about 50% of the hot water requirements of a house ( according to various sources ). This means that there is the potential saving by installing the system of about 150 euro. In most solar water heating systems there is a small circulating pump that would cost in the region of 50 euro per year to run. This means that we could potentially save approximately 100 euro per year using a solar water heater.
A plumber I know well quoted us 2,200 to install a small 2m2 tube solar water heating system. This would qualify for a grant of 600 euro, leaving a cost of 1,600 to pay. Recouping the cost at 100 euro per year means that it would take 16 years to recover the cost of installing the system.
The manufacture of solar hot water systems is most likely done using traditional energy sources and the materials aren't "sustainable". I'm not convinced about solar panels
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There are a few points to this though;enquiringminds wrote: »We have a new condensing boiler and a 190l stainless steel cylinder with a dual coil ( suitable for solar panels ). We currently heat our hot water using the gas boiler. During the Summer, when the heating wasn't being used I monitored the gas usage to estimate the annual cost of heating the hot water. This figure came out at approximately 300 euro.
A solar water heating system typically provides about 50% of the hot water requirements of a house ( according to various sources ). This means that there is the potential saving by installing the system of about 150 euro. In most solar water heating systems there is a small circulating pump that would cost in the region of 50 euro per year to run. This means that we could potentially save approximately 100 euro per year using a solar water heater.
A plumber I know well quoted us 2,200 to install a small 2m2 tube solar water heating system. This would qualify for a grant of 600 euro, leaving a cost of 1,600 to pay. Recouping the cost at 100 euro per year means that it would take 16 years to recover the cost of installing the system.
The manufacture of solar hot water systems is most likely done using traditional energy sources and the materials aren't "sustainable". I'm not convinced about solar panels
You already have a well insulated cylinder. This is normally part of the cost of installing a solar water heating system. Not so in your case. Also, you have a very efficient boiler (but everyone should be doing that bit).
The solar panel you were quoted for would barely meet 50% of your water needs. I would prefer to put that labour into putting in a properly sized panel which would meet up to 70% of your water needs, but at least 60%, and probably with no change in price because the cost of additional tubes are usually more than covered by the cost of the grant.
Your pump would only cost about €10 per year to run, if that. Nowhere near €50.
Add to that the likelihood that gas prices will rise over the lifetime of the system, and it starts to make a heap of sense.
You are now saving about €200 per year for a cost of €2,200, and that saving will rise with energy costs. You've improved the BER rating of your house, and its resale value. And you have the satisfaction of getting most of your water from the light instead of burning fossil fuels from Siberia.0 -
Hi Quentin,
I think you're right about the size of the system. There are guidelines about sizing the system given the number of people in the house. Typically 1m2 per person, I think. The <SNIP> website recommends 100l of storage for each square metre of tubes.
<SNIP>
That limits us to 2m2 of panels, as our cylinder is only 190l. On the same page, which is quite old, you can compare the prices for a 2m2 panel system and a 3m2 panel system. There is a difference of 800 pounds between the two.
The figure of 50% that I gave is a reflection of what is in literature:
http://www.seai.ie/Renewables/Solar_Energy/Solar_Heating_at_Home/
If we use the figure of 60% and the pump was free, that would mean the system would save potentially up to 180 euro per year. If I install the larger system it would cost in the region of 5,000 euro per year and earn a grant of 300x4 = 1,200 euro. That would mean 3,800/ 180 = 21 years.
Mod Edit: Please don't name or link to a specific company on thread.0 -
Some companies use a smaller solar panel per L of water to reduce the need for a heat dump. If you size your panel so that it provides enough hot water for the household in September and March, it will produce an excess in May to July. I prefer to over-size the panel, maximise solar gain, and use a heat dump radiator to get rid of the surplus. That way you can get up to 70% of hot water provided by solar at not much more cost.
In relation to your cylinder, while it is on the small side for solar panels, provided your water isn't too hard (limescale forming..) you can heat the water in your cylinder to 85 degrees and use a blending valve to bring it to a safe temperature at the taps. 190L of water at 85degrees stores the same amount of "heat" as 285L of water at 60 degrees.
Installing a larger system onto your existing cylinder should't cost you a penny more than the 2M system. The panels will be an extra couple of hundred and the grant will more than pay for the difference.0 -
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Quentin,
There are a host of issues with your post.
The first is the introduction of a dump valve to gain 10% of our hot water costs. 10% of our hot water cost, for a house with 4 adults, is 300 x 0.1 per annum, or 30 euro. How can you justify oversizing the system and plumbing up a dump rad for 30 euro per annum? That's assuming that the system provides 60% of the hot water requirements during the year, which is already at the top end of seai projections. During the Summer we don't require heating and therefore I'd expect that a rad that heats then would be wasteful. It is also most likely that the rad would heat during the day, when heat wouldn't be required. The idea of wasting energy like that to try to save heat just doesn't add up to me...
My second issue is similar to the first. Storing water at high temperatures is costly. The losses are greater due to heat loss, poor heat exchange efficiencies, and it creates the requirement for an anti-scald valve. We aren't limited by the size of our cylinder as it is, and we store water at a relatively low temperature.
I've done the rough calculations for a smaller system, and I've done the rough calculations for a medium system. There is a grant of 300 euro per m2 for tube systems up to a max of 6m2. If we installed the biggest system possible it would most likely cost about 6k. The system you are talking about would probably cost more. The grant would then be 1,800 euro. That would leave 4,2k to recover. Let's say the system performed even better than you predicted and gave 80% of the hot water requirements. That's 300 x 0.8 = 240 per annum. That would take over 17 years to recover. That's not including the cost of the pump to run the system.. Have you ever heard of NPV?? Also bear in mind there may well be a decrease in efficiency of the system...
There are two additional things to consider. The first is that we would consume a large amount of goods and services to come up with 4,2k to pay for the system. We try to be good to the environment but we still eat, drink, drive, work, travel, wear clothes etc. ( not necessarily all at the same time...) So, we have an impact on the environment to put this money together.
The second is the rising cost of energy. If you can predict the price of energy, then I would suggest that your talents are wasted selling solar water heating systems.
To answer the OP's question, 60% of the energy consumed in the home is consumed for space heating. 25% is consumed for heating hot water and the remaining 15% is consumed on electrical products, such as fridges, lights, etc. These proportions give a good starting point on where to increase efficiency. Imagine, if you save 10% on heating, it's the same as almost halving your hot water energy consumption.... food for thought. Another interesting thing is that we consume 3% of our energy on lighting. I don't know about you but every light we have is energy saving
The energy saving trust has a lot of information about what to focus on.
http://www.energysavingtrust.org.uk/
There are documents in the homeowners section, and if you're feeling brave you can look into the Business and Public Sector tab. There is a scary amount of info in there. It was a real eye opener for me. The two main areas to focus on, as far as I could see, were insulation and heating.0 -
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Poor Uncle Tom,
I've done a little reading and I agree that a heat dump is a good thing to have to protect a solar system, particularly if the system is oversized.
Quentin,
wasting energy..
I just got a price of 1,880 for a 2m2 system and a price of 2,300 for a 3m2 system, ex labour. That's a difference of about 420 per m2. So, I agree that the grant covers most of the difference in size. I'm pretty sure there was no cylinder included in the quote.
storing water..
I agree that an anti-scald mixing valve is good practice to have, although I also believe that the efficiency of the heat exchangers go down as the storage temperature goes up.
Costs...
Our plumber was looking for 400 euro to install the system. Our roof faces SW, so we could probably accommodate a larger panel but the efficiency would be reduced.
energy consumption...
that may be true to some extent and a generalisation is always open to exceptions. In our particular case I think our heating and hot water costs are almost equal. We have a pressurised system and the occupants have somewhere between 4 and 5 showers per day. We recently insulated the whole house and installed new windows and doors. Add to this improved heating system and controls and our heating costs are quite low. That reminds me to track our heating costs.
Areas to focus on...
I'm glad we've found a common ground
. I'm not against solar by any means, but like you, I think people should focus on areas where they can make the biggest savings. Once those areas are addressed then people can look at where they may make more savings. 0 -
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As an aside, and a solar user myself, I'm aware that the numbers don't, won't, always stack up. There's always some part of the equation that everyone will pick up on. Cost, Installation, Running, Maintenance. Take your pick.
So, sticking to costs, we could make the sweeping statement that, effectively done, payback is anywhere from 6 - 16 years, depending on your point of view. And, if I row in the capital amount we're talking about - let's say 2500.
Right, look outside your front door.
Now, tell me, how much depreciation did your car suffer in the last year ??
So, even a very modest car, would lose 2 k in a year, and go upwards. May I suggest you drive your car for just 1 more year than normal, before changing it, and now: your solar is paid for. Q.E.D.
Next ??
And if, in doing so, your driving habit has been changed once, maybe it'll stick, and you can extrapolate your 10 yr motoring savings, and offset them against whatever you want. Or, just send me a cheque........ Ode To The Motorist
“And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road”
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So, even a very modest car, would lose 2 k in a year, and go upwards. May I suggest you drive your car for just 1 more year than normal, before changing it, and now: your solar is paid for. Q.E.D.
Next ??
And if, in doing so, your driving habit has been changed once, maybe it'll stick, and you can extrapolate your 10 yr motoring savings, and offset them against whatever you want. Or, just send me a cheque........
This is a false dichotomy - just because you've made a saving on the car depreciation, doesn't necessarily mean it's sensible to spend it on a solar system. (Which itself would be depreciating in value, albeit at a slower rate than the car!)0 -
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The possible cash savings on solar hot water, whatever way you slice and dice the numbers, never seem to get close to coming under the 10 year threshold beyond which trying to extrapolate both energy prices and future household hot water use get increasingly into the realms of mere speculation.
That said, as Quentin often points out, it's not all or even mainly about cash, it's about leaving a habitable world for our children and theirs. It's rare, though, to see estimates for the environmental payback on solar hot water systems, in terms of CO2 emissions avoided, which take into account the embodied CO2 and energy in the solar system itself. Can you shed any light on this Quentin?
Gizmo,
strictly speaking this is off topic although I think you've raised a relevant issue. Here's my ( unsolicited ) ramble on your post and others:
Energy efficiency improvements are best made in an orderly fashion. For example, it doesn't add up to say that because heating their hot water is expensive, a person should install a solar panel as the first course of action.
Installing a solar panel has a long, potentially infinite, economic payback in my opinion. I believe that it would take us well over 20 years to recoup the cost of installing a solar panel. For other people it may never happen. It is way down the list of things people should do to make their homes energy efficient. Bear in mind that the general advice is to replace a boiler every 10 - 15 years. That will bring increased efficiencies and skew the picture.
If we take harmful CO2 emissions in the same light. We should look to see which area globally produces most CO2 emissions. If that is the case, I would suggest that domestic solar panels are way down that particular list.
Here's my opinion on solar panels and CO2 emissions ( again unsolicited )
1. I was shocked at how little it cost in monetary terms to heat hot water for a house of 4 adults using a modern, efficient system. I'd guess there is a CO2 emission figure related to natural gas.
2. The cost to the environment of going solar starts with an individual making/ saving/ borrowing :eek:/ selling their car to the tune of a solar panel system. According to the SEI website the cost is 4,000 to 6,000 euro. Let's assume the individual doesn't downgrade to a banger to afford the panel and that they work for the money. I think that is reasonable to do as work is the main source of income for people. So, if a person has a carbon footprint to make money then we should multiply that figure by whatever the cost of the system is. Let me point out at this stage that old cars have higher CO2 emissions.
3. The second "cost" to the environment is the cost to manufacture the solar system itself. That should include all the associated related activities, such as advertising, manufacturing, installation, etc, etc. Think of all those footprints.
4. The third "cost" could be the running and maintenance of these systems. They typically have an electrical running cost and require routine maintenance, don't forget.
5. The fourth "cost" should be an allocation required of the traditional system used to support the solar system. SEAI website reckons 50 - 60% of hot water is provided by the solar system, so the traditional heating system provides the rest, or we have cold showers in the winter.
6. The fifth "cost" could be the grant that is provided by the government. The government isn't solar powered afaik. So, that'll be, say, 1,800 aggregate taxpayer carbon footprints.
Now, I'm no wizz on calculating or adding footprints but my bet is the environment would be happier without solar panels....
Just today, I got a small bag of what I think are wood pellets today from the SEAI. What happens to the picture if I decide to install a biomass boiler? AFAIK one of the main effects is that it will exacerbate the world food shortage as farmers grow less food in order to produce biomass crops.:eek:
A friend of mine pointed out this evening that trees and plants consume carbon dioxide...
Mod Edit: I will repeat myself just this once, STAY ON TOPIC.0 -
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