Does anyone have solar water heating?

[Laura Corin]

We probably need to replace our gas boiler, which heats our water as well as powering our central heating. There are two main types of system in the UK; we are thinking of changing to the other kind in order to be able to install solar water heating panels in the future. These would feed into the water system, so that the gas boiler would top up the heat if it was insufficient. We have been told by many people that they work well in this area, providing large amounts of heated water, even in winter.

 

Does anyone have any experience? The solar-compatible boiler system would be more expensive, so we want to make sure that it is not wasted money.

 

Thanks

 

Laura

[RegGuheert]

We decided to invest in solar this winter to take advantage of some of the incentives now available in the U.S. Our original plan was a fairly large grid-tied solar-electric system and a solar water heater. At the end of the day, we balked at the $11,000.00 price tag for the solar water heater and decided to put all of our investment into a larger solar-electric system. Why? IMO, solar water heaters are very much Rube Goldberg contraptions with very little chance of long-term reliability and therefore little chance to repay the investment. By contrast, our new micro-inverter-based grid-tied photovoltaic system promises to pay back its investment in 5 to 6 years and provide a steady stream of cash and electricity thereafter.

 

That said, I am currently designing the energy systems for an entirely off-grid home which my sister and her family are building. Included in this system is a solar water heater which provides both domestic hot water and space heating for the entire house. The system is backed up by propane for the times when it is too cold and/or there is too little sunlight to heat the entire house. The house also has an impressive custom-built Swedish fireplace.

 

I would like to give you two cautions about what you are considering:

 

Caution 1: Solar space heating tends to be one of the least affordable applications of solar energy that there is. Why do I say this? Because you do not need space heating systems for more than about half of the year, maybe even less. On top of that, you need the solar energy during the portion of the year when you have the LEAST sunlight and the outdoor temperature is the lowest. The result is that you need a very large and quite advanced collector in order to provide heat for a meaningful percentage of your house's heating needs. Then you need to carefully design the system so that it will NOT collect nearly as much heat during the non-heating months.

 

Caution 2: I think of the U.K. as a place that has a lot of overcast skies. While I am sure that is not true all of the time, you should ask yourself how much sunlight you receive in the wintertime. If it is cloudy a lot during the winter, you probably should not consider solar for your space heating application. As an example of the important effect climate can have, I have been comparing the electricity generation of our recently-installed solar-electric system with one of similar size which was installed in Seattle in early October. In eleven days, our system has produced 332 kWh of electricity while the system in Seattle has produced 593 kWh of electricity in approximately three MONTHS. In other words, our system is producing an average of SIX TIMES as much electricity each day as the slightly-larger system in Seattle. That difference is largely due to the different amount of sunlight that falls on our roofs in the different locations.

 

If you would like to push on and would like some ideas on possible ways to proceed, please let me know and I would be happy to give you some of my thoughts.

 

Good luck with whichever way you go!

[Chris in VA]

Wow, Reg--that was a neato keeno answer! I'm so impressed!

 

I was just going to say that my mom and dad had a solar water heater when we lived in FL, about 30 years ago. It worked very well.

 

That is all.

 

:D

[Laura Corin]

Thanks, Reg. The solar heating would only be for water for showers, etc. The central heating for the house is separate. As you say, we don't have enough light in winter to heat a house, but in summer we have up to 21 hours of daylight to heat water for washing. I have looked into photovoltaic cells, but the investment would be enormous. The UK provides incentives for both kinds of solar power collection.

 

Laura

[RegGuheert]

Hi Laura. Sorry, I misunderstood your message (obviously!).

 

In any case, I have looked into solar water heating for my own usage and so far I haven't felt the cost was justified here in VA. Even though photovoltaics are much more expensive to install, they are arguably much more reliable (when grid-tied) and there are significant additional incentives that apply to PV (again when grid-tied) that do not apply to solar water heaters.

 

I found a map of UK solar insolation here. The units in the monthly chart at the bottom are kWh/m^2/day. This unit is also known as "full-sun hours per day." Another way of thinking about this unit is to think of it as the unobstructed sun being directly in front of your collector for that many hours each day and dark the rest of the day. (Although in reality the energy is spread over a larger amount of time.) I will say these numbers are *very* low. In December and January, you are receiving about 0.5 full-sun hours per day. Where I live, we receive about three full-sun hours per day during those months, or about 6 times as much sunlight. In the summertime, your numbers are 4 versus 7 here, so again it is lower.

 

I have never been able to quite justify solar water heating here, even with tax incentives, so I would say that your energy costs would need to be about three or four times what ours are in order to justify the expense. That may very well be the case, but I don't know the numbers to compare.

 

I will say that there are many ways to save money on water heating that do not include solar collectors. These include tankless water heaters (gas or electric), heat-pump water heaters and hybrids of various sorts. In fact, I have just invented a simple hybrid water heating system which should give all of the energy savings of a tankless water heater without requiring the 30 kW(!) of power to run it, as the electric ones in the US do. Instead this system only requires 7.2 kW. I am considering commercializing this idea, as I think it would be attractive in many applications.

Edited January 16, 2011 by RegGuheert

[Laura Corin]

Thanks, Reg. Last year we spent £2,800 on gas for heating/water heating of our four bedroom house. We don't keep the house hot - around 16 degrees C is comfortable for us. We have to use LPG gas, delivered to our underground tank by tanker, as we are too far from piped gas supplies. We have just had our roof insulation improved and our cavity walls insulated. We supplement our gas heating with a wood stove (we have our own limited wood supplies). We are also switching to a cheaper gas supplier.

 

We currently have a twelve-year-old tankless boiler. We are planning to upgrade either to a tankless ('combi') condensing boiler, or a condensing boiler with a separate tank. The former is not suitable for the solar water heating; the latter is but would cost £1,000 more. Either would will take our fuel-use efficiency from 76% to over 90%. Our boiler is broken at the moment and I don't want to invest much in getting it fixed; we spent a lot on fixing it last winter, so I think that it's time to move on. Hence the pressure to make a decision about which system to go with.

 

ETA: we are being quoted £8,200 to install the solar water system, in addition to the £1,000 for the compatible heating system. The returns (these are based on assumptions that the government produces to go along with its incentives, not an optimistic forecast from the salesman) would be £1,200 to £1,500pa, including government incentives. The latter are likely to last for 20 years, but the final news on this will be announced next month. So, we are talking about over a 10% return on our investment with the solar water heating.

 

Thanks again

 

Laura

Edited January 16, 2011 by Laura Corin

[RegGuheert]

Thanks, Reg. Last year we spent £2,800 on gas for heating/water heating of our four bedroom house. We don't keep the house hot - around 16 degrees C is comfortable for us. We have to use LPG gas, delivered to our underground tank by tanker, as we are too far from piped gas supplies. We have just had our roof insulation improved and our cavity walls insulated. We supplement our gas heating with a wood stove (we have our own limited wood supplies). We are also switching to a cheaper gas supplier.

Ugh! Propane gas is about the most expensive energy source available around here. We put in a 100-gallon tank when we built our off-grid PV system 12 years ago. Since then the price of LPG has skyrocketed to over US$4.00/gallon. I'm guessing you pay a lot more than that given the relative price of gasoline between the US and the UK!

 

£2,800 is a lot of money for heating and hot water! At that price I would say solar should start to become affordable.

We currently have a twelve-year-old tankless boiler. We are planning to upgrade either to a tankless ('combi') condensing boiler, or a condensing boiler with a separate tank. The former is not suitable for the solar water heating; the latter is but would cost £1,000 more. Either would will take our fuel-use efficiency from 76% to over 90%. Our boiler is broken at the moment and I don't want to invest much in getting it fixed; we spent a lot on fixing it last winter, so I think that it's time to move on. Hence the pressure to make a decision about which system to go with.

Wow! I hope you have a source of heat!

ETA: we are being quoted £8,200 to install the solar water system, in addition to the £1,000 for the compatible heating system. The returns (these are based on assumptions that the government produces to go along with its incentives, not an optimistic forecast from the salesman) would be £1,200 to £1,500pa, including government incentives. The latter are likely to last for 20 years, but the final news on this will be announced next month. So, we are talking about over a 10% return on our investment with the solar water heating.

£8,200! And I thought US$11,000 was bad! I'm thinking everything is more expensive in the UK! One thing I didn't say previously is that I can buy the parts and install the solar water heater myself for US$5500. We could still go this route, since we can get 30% back from the government, making the cost around US$4000 plus bits and pieces I may need to purchase. Perhaps you could pursue a similar option to save money?

 

I'm wondering about the system which has been specified for £8,200. Did they quote an evacuated tube collector system? If not, I would be concerned that the system would have TERRIBLE performance during the cold months. If so, how many tubes are they proposing? 40? More? (FWIW, the vendor is installing a 120-tube system at my sister's house for US$22,000 next month. That is for BOTH space heating and domestic hot water. It's gigantic! I hope it is not TOO unattractive. I can post a photograph once it is installe.)

Thanks again

 

Laura

You're welcome! Good luck getting your new boiler installed! I'm sorry about that. I absolutely HATE forced expenses like that! :tongue_smilie:

[LisaKinVA]

Have you thought about a geothermal (you could use the diagonal-well style, which is made for small lots), and then you could get hot water off of that. My dad switched from a standard heat pump to geothermal 18 months ago. With 10 of us here, he hasn't had his electric bill go higher than $400 -- which includes the hot water. Prior to the geothermal, he spent about $800 a month for heating, and $700 for a/c.

 

We will be doing geothermal in our new house as well.

[RegGuheert]

Have you thought about a geothermal (you could use the diagonal-well style, which is made for small lots), and then you could get hot water off of that. My dad switched from a standard heat pump to geothermal 18 months ago. With 10 of us here, he hasn't had his electric bill go higher than $400 -- which includes the hot water. Prior to the geothermal, he spent about $800 a month for heating, and $700 for a/c.

 

We will be doing geothermal in our new house as well.

I investigated geothermal heat pumps very carefully for my sister's new home and ultimately I decided that the electrical load was too great for an off-the-grid home. That doesn't mean it is a bad choice for an on-grid home, however.

 

Do you know what the HSPF and SEER ratings of your father's OLD heat pump were? I suspect the energy comparison you are making is between a modern, new geothermal heat pump and an old, antiquated heat pump, which may not give a fair picture. I suspect if you compare the two modern units the performance is quite similar, with the heat pump costing less than half what the geothermal system costs. OTOH, the geothermal heat pump is typically quieter and should last longer.

[Amber in AUS]

Laura, I just wanted to comment that we had a solar hot water system at our last house with a gas booster. It was awesome! We never, ever ran out of hot water. The gas was only ever used when the water wasn't hot enough, so just to boost the system along. I'd have another no problem at all. The reason we don't currently is that we moved into an established house and the hot water system here is brand new, no excuse to replace it at the moment :D

[happygrrl]

 

That said, I am currently designing the energy systems for an entirely off-grid home which my sister and her family are building. Included in this system is a solar water heater which provides both domestic hot water and space heating for the entire house. The system is backed up by propane for the times when it is too cold and/or there is too little sunlight to heat the entire house. The house also has an impressive custom-built Swedish fireplace.

 

 

 

Reg- We have lived of the grid for 13 years now. We started with candles and kerosene lanterns and now have grown to internet... the history of technology in just a little over a decade! Anyway- our current system is maxed out and I know that things have really changed in the years since we bought it. Would you mind if I pm'd you with a few questions? I am especially interested in getting all our systems working together to become even more self-reliant. Thanks!!! ~ Lisa

[RegGuheert]

 

Would you mind if I pm'd you with a few questions? I am especially interested in getting all our systems working together to become even more self-reliant. Thanks!!! ~ Lisa

Not at all. Please do.

[Melissa in Australia]

We have had solar hot water for 10 years. It took 4 years to pay for itself. now we have completely free hot water. We don't have booster turned on/ We manually switch it on for the few days we need to heat it. mind you, we have lukewarm water in winter ( we are ultra frugal).In spring, summer and autumn it boils.

 

DH is going to connect it to my combustion stove this summer so we will heat that way in the winter. It was connected to our old wood heater, but when we remodeled 3 years ago, we took it out

[TheReader]

I don't know any of the technical stuff, and obviously the amount of sun I get in Brazil (inside the tropic region) vs. the amount you'll get in the UK is likely different, but we have solar water heater. Ours is solar panels on the roof, and the water runs through the panels (well, there's a tie-in or something, and the pipe goes through the infrastructure of the panels...??) Anyway, however it works, it works quite well. We do have an electric water heater for back-up -- we keep the breaker for that turned off and just turn it on as needed.

 

I will say, with ours, during the winter we need to use the back up as much as once/week or so, as the water cools down too much in the tank and then it's not able to heat up enough. (or something like that). IN the summer, which is also rainy season, we have to use it only if it's been cloudy all day long for weeks on end. For ex, it's been raining most of the day all month, but we've had bits and spurts of sunshine. We only just in the last 2 days had to turn on the back-up, and were able to turn it off almost immediately as the sun came out and took over.

 

So I guess I'd say it partly depends too on if you'll have a water tank collecting the solar heated water, and if that then will cool down in the winter, in which case you'll likely use your back-up quite a bit.

 

Mostly I love ours and hope we can do something similar in the US. We have saved a ton on energy bills in this house. (my 2nd choice for the US would be the tankless, "on demand" hot water heaters; we had that in our apartment and LOVED it).

[nd293]

Our rented house had an electricity-boosted solar hot water system. In summer the water was always hot. On a sunny winter day in Australia the solar system worked fine, and we managed even on the odd cloudy days. Several cloudy days in a row resulted in only tepid water (we discovered this by accident as the booster had tripped). We will eventually switch to gas-boosted solar hot water in the house we bought. They're very common here, and I've never heard anyone complain.

[LisaKinVA]

I investigated geothermal heat pumps very carefully for my sister's new home and ultimately I decided that the electrical load was too great for an off-the-grid home. That doesn't mean it is a bad choice for an on-grid home, however.

 

Do you know what the HSPF and SEER ratings of your father's OLD heat pump were? I suspect the energy comparison you are making is between a modern, new geothermal heat pump and an old, antiquated heat pump, which may not give a fair picture. I suspect if you compare the two modern units the performance is quite similar, with the heat pump costing less than half what the geothermal system costs. OTOH, the geothermal heat pump is typically quieter and should last longer.

 

Our neighbors with propane pay $1000 a month to heat (home is under 5 years old); our neighbors in a similar sized house with an energy efficient heat pump pay about $500/month to heat (they don't have as many people in their house... my dad's electric bill should drop to about $150-200 a month when we leave).

[Laura Corin]

We are havering because our current gas boiler produces instant hot water. We can have as many showers in a row as we like, or baths if someone wants. We can't have showers simultaneously, but we don't find that hard to manage.

 

Those who are using/have used solar water, how big is the tank and how many showers (or baths) can you get out of it when it's hot - either from solar energy or from the booster? If you use the booster, how long does it take to reheat?

 

Thanks

 

Laura

[TheReader]

We are havering because our current gas boiler produces instant hot water. We can have as many showers in a row as we like, or baths if someone wants. We can't have showers simultaneously, but we don't find that hard to manage.

 

Those who are using/have used solar water, how big is the tank and how many showers (or baths) can you get out of it when it's hot - either from solar energy or from the booster? If you use the booster, how long does it take to reheat?

 

Thanks

 

Laura

 

I don't know the size of our tank. It's big by US standards, small to medium by BR standards, and no idea how that compares to the UK.

 

Yesterday I had one in the tub (filling a deep tub) and one in the shower at the same time. ON a normal day, we can have 4 showers in a row and still have plenty of hot. I wash dishes by hand, too, and can be doing that while the boys shower and it's not a problem.

 

We actually have longer-lasting hot when using just the solar; with the booster, it is coming out of the tank; with the solar panels, I *think* it's heating at the source (heating as the water passes through the panel/tie in thingy) (I think).

 

When we are using the booster (electric in our case), it takes about 2 hours to re-heat; I have to turn it on at least 2 hours before we need it. With that, because that's coming from the tank, the 4th shower is getting cool; we make sure when using the booster that our middle son goes last as he likes his water cooler than the rest of us. Still warm, but cooling down.

 

But on just the solar we've never run out of hot. Our youngest likes to stay in the spray of water and play and play and play -- we've had him in 30 minutes past the last person (so, running hot water for probably an hour total) and still have hot water when he gets out. I could still, at that point, come downstairs and wash dishes with hot water and it would be fine.

 

If your solar panels are the kind where the water ties into the panel/passes through the heater right there, your experience would likely be similar.

[Melissa in Australia]

We can have 7 showers in a row in summer without any reduction in temp of hot water. In winter 3 showers will make a difference. We turn the booster on at night, it takes about 3 hours to heat it up from cold. the newer type systems apparently work better on cloudy days. We have a system that has copper pipes enclosed in a glass panel. the copper pipes have a mix of glycol and water, it then goes into a heat exchange unit, and heats up the water that goes into the hot water system. The newer systems have vacuum cylinders and are more efficient.

 

We have very short showers because of limited water in general we are not connected to mains water.

[Laura Corin]

Our plumber confirmed this evening that the current boiler would cost a lot to fix, so we are definitely getting something new. We are getting quotations for both kinds of systems, but are seriously considering the solar-compatible one.

 

Thanks again,

 

Laura

[happygrrl]

Not at all. Please do.

 

Thank you so much! I told dh about your set up and he was quite interested in hearing more. It might be a while, as we are experiencing major rain and days are taken up with ditch digging!

[RegGuheert]

Our plumber confirmed this evening that the current boiler would cost a lot to fix, so we are definitely getting something new. We are getting quotations for both kinds of systems, but are seriously considering the solar-compatible one.

 

Thanks again,

 

Laura

Please let us know what the quotes look like and which way you go!

 

A couple more thoughts:

 

- Solar thermal technology seems like such a "no-brainer" (and it really is in some climates), but where I live it is not common, yet. Where you live, the solar resources are quite minimal, but the energy prices are very high. It becomes much more complicated when there isn't much sun and the temperatures outside are low.

 

- My advice to my sister has always been, and continues to be, that the key component to an off-grid renewable energy system is providing a practical means to store the energy. For solar thermal, it is the "thermal battery", for solar electric, it is the chemical-electrical batteries. Once these are in place along with a way to use the energy from these "batteries", you can always augment your system in the future with ways to get energy into your "battery". In her case, the thermal energy for space heating is stored in the concrete slab under the basement floor. Heat for domestic hot water is stored in an insulated tank, just as yours will be.

 

- I ran across the Green Energy Advisor Blog while researching my sister's system. I will say it is a fascinating compilation for anyone interested in that subject. Some of the technology there blows me away. Interestingly, they absolutely poo-pooed the approach I used for my sister's home, but they sometimes have posts expressing both exactly OPPOSITE opinions on the very same subjects. IMO, the jury is still WAY OUT on how to address may issues in the world of energy and it is very interesting to see so many different ways!

 

I hope all goes well and your system doesn't break the bank!

Edited January 19, 2011 by RegGuheert

[Laura Corin]

- Solar thermal technology seems like such a "no-brainer" (and it really is in some climates), but where I live it is not common, yet. Where you live, the solar resources are quite minimal, but the energy prices are very high. It becomes much more complicated when there isn't much sun and the temperatures outside are low.

 

Is pre-heating. In the summer (it seems) you can get around 85% of your hot water needs from solar. Bear in mind that UK washing machines heat their own water, so the only draw on the hot water system is washing people. In winter, the solar energy heats the washing water up to the double digits centigrade, as opposed to the low single digits, as it is in the pipes; the boiler then kicks in to heat that water to a useable temperature. Given the price of fuel (especially as we have to use LPG) this may well be worthwhile, when combined with government subsidy. The latter is still moot: an announcement is expected next month.

 

We are considering photovoltaic cells and (more likely) wind power in addition, as we have an open aspect to the prevailing wind and fairly high wind speeds. The solar water heating idea has been brought to the forefront by the failure of the boiler.

 

Thank you again,

 

Laura

[RegGuheert]

We are considering photovoltaic cells and (more likely) wind power in addition, as we have an open aspect to the prevailing wind and fairly high wind speeds.

Since you have uttered the W-word, I am forced to provide you with the following links: ;)

 

The following link is a *recent* survey of current-technology wind turbines showing *actual* production in a decent wind environment:

Comparison of 12 commercially-available small turbines

http://www.theoildrum.com/node/6954

 

 

The next link is rather dated, but what struck me about this link was the fact that this man was a major wind enthusiast, but his three installations failed in about every way imaginable. He also has some recordings of the screaming sounds that small wind turbines can make.

Wind Turbine site from someone at North Dakota State University (Check out the audio)

http://www.ndsu.nodak.edu/ndsu/klemen/index.htm

 

My personal opinion is that wind energy is a GREAT solution for utility-scale renewable electricity generation and photovoltaics is a GREAT solution for home-scale renewable electricity generation. On the flip side, I feel that wind is a POOR solution for home-scale electricity production and PV is a POOR solution for utility-scale electricity production.

 

Since you have fairly poor solar insolation, that doesn't leave any obvious solutions for your location. Wind may very well be your best solution, but I will give you a very strong CAVEAT EMPTOR before you purchase a small-scale wind turbine.

 

Just a little anecdote about my very limited personal experience with wind energy: One of the solar contractors who bid my sister's job suggested the inclusion of a wind turbine in the system. I then told him my rather-negative views on that approach and that we were not likely to go that route. After the meeting, we went on a little tour of a couple of his installations, including one at my sister's friend's house which included two wind turbines which had been turned on for about two months. When we arrived at the site, there was a steady breeze. One of the turbines was turning and the other was not. Although he tried to explain away that condition, he did nothing to improve my view of this technology. :glare:

 

Just by way of interesting wind energy generation ideas, here is a technology invented in Italy which produces electricity using a kite-flying robot. Again, I think this is a utility-scale solution, but I found it to be quite interesting.

Generating electricity from wind by flying a kite

http://europe.theoildrum.com/node/7014

http://www.kitegen.com

 

Again, good luck with your boiler upgrade project!

 

BTW, as an aside, I have noticed when traveling in Europe that one of the national pastimes in Britain seems to be disparaging contractors who do work on people's homes (sorry, I forget the word you use for them there). Seriously, I could not believe the vile things that people were saying about these contractors. To that point that it sounded like a form of racism! It struck me because I cannot say that I have noticed any similar widespread negative view of tradesmen in the US. Personally, I am constantly amazed by how quickly and professionally these people can perform a task that I KNOW would take me an inordinate amount of time and would not be done nearly as well. And I consider myself to be quite handy!

 

So I am wondering, was what I saw just another form of sensationalism being foisted on me by some reality TV shows, or is there really a general negative view of contractors overcharging and doing sloppy, incomplete work in the UK?

Edited January 19, 2011 by RegGuheert