Big Steps in Building: Put Solar Hot Water Heaters on Every Roof
by Lloyd Alter, Toronto on 03.17.08
How dumb is this? Use coal to boil water. Use steam to spin turbines and run generators to make electricity then transported long distances to connect to a coil at the bottom of a tank- to make hot water.
Solar hot water panels are dumb simple too, often just a box with a glass lid with black pipes in it; you can even build them yourself. Others, like evacuated tube collectors are more efficient if more expensive.
A solar water heater could save $ 450 a year and keep almost a ton of CO2 emissions out of the air; multiply that by 80 million houses in the USA. The technology has been around forever. Chinese manufacturers are cranking them out by the millions. So why doesn't every house have them?
evacuated tube solar hot water heater with tank
Eco-geek suggests that "First, installation can cost more than $5,000 dollars, especially in older houses. Second, new home buyers apparently don't like to see solar water heaters disrupting their "roof lines."
In other countries they are common; in some, like Israel, it's the law. Some cites encourage it; the City of Fresno provides rebates and financing. It isn't just for the sunny south, either;
Solar hot water is the cheapest and most effective active solar power system there is. It leaves fossil fuels and electricity for uses that require a higher grade of heat. Let's put it in the building codes. ::Eco-Geek
Where i live, in Bangalore India, this is not an uncommon sight at all (i mean the solar panel on a roof, not the snow :) ) Since there is such a plenitude of resources in the west they are slow to look for cheap alternatives, whereas in the developing world, it is a paucity of resources rather than environmental factors that spur people on to look for alternatives to traditional energy sources.
People are more focused on granite counter tops and the like, so don't bother to educate themselves about such things.
the payback period on solar hot water heating is relativly quick, much faster than for solar photovoltaic.
Now that energy prices are rising, maybe people will start to pay attention to these sorts of things.
Spot on! It had seemed to me that hype and efficacy of solar tech is inversely related.
I definitely want one when I have a roof to put it on. Makes so much sense.
Plain, dumb, simple, cheap. The last item is probably the reason it doesn't receive much support and probably won't in the near future. We can only hope that there will be a groundswell of support for renewable energy sources. I posted a video on my site that shows a women discussing alternative energy that completely changed my outlook. Wind , wave, and solar energy aren't really alternative at all--they are the most obvious and largest sources of energy on the planet. and are renewable as well.
I would love to have one and I even have a portion of my roof that points almost south, but I just can't justify $3k to $5k for purchase and installation to offset the $30/month it costs me in natural gas to heat our water. Besides, the $5k won't get me 100% of my hot water. It mostly supplies the hot water when I need it least - in the middle of the day. So if it reduces my gas bill by 50%, it will take 27 years to recoup the cost. I'm all for it, but the up-front cost is a tough pill to swallow.
My uncle just got a solar water heater. The good man took my advice and installed a heat-exchanger on the shower drain so the hot shower water can pre-heat the water leading up to the tank! Savings all the way.
Down here in Texas our attics could be used for pre-heaters for DHW. All we need is for someone to develop one that can be installed inexpensively to pre-heat the hot water going to the tank
Solar hot water sounds great in theory, and I'm sure it works well. But I asked for a bid to replace my aging gas fired model and received an estimate of $10,000 (US). I would love to do this, but with 3 kids, how can I possibly justify that price? If someone knows how to do it cheaper in northern New England, let me know.
Randy - you need to get a new estimate. That $5000 should net you 80%+ of your annual DHW needs, and it would be available 24/7, not just in the middle of the day. You could even shoot for 100% coverage for a little more, but that would require "dump loops" for the summer.
Tim - those hot attics shouldn't exist to begin with. Proper application of steel roofing and/or radiant heat barriers would eliminate hot attics.
"Tim - those hot attics shouldn't exist to begin with. Proper application of steel roofing and/or radiant heat barriers would eliminate hot attics."
While there are a lot of things that can be done to reduce the heat in attics, you have to realize in Texas the AMBIANT temperature can be as high as 100 degrees, and can stay in the high 90's for several months.
Even a well vented attic will still be hot if the ambiant air is that hot, not to mention the heat gain from the roof.
White roofs should become standard IMO.
We're finalizing our plans for a new ICF house in Virginia. We are installing on-demand water heaters (propane) so it's tough to justify solar hot water for that alone. However, I'm putting in-floor radiant heat in the basement slab, in my garage workshop, and the bathrooms (cold tile is not fun to wake up to).
I also plan to pre-heat the hot water before it gets to the on-demand heat. Certain models modulate the heating based on the temp of the incoming water so that saves some on the fuel cost.
If that's not enough, I will use this to provide or assist in providing hot water to a hot water coil in my HVAC for those cold days when the heat pump can't keep up.
I was planning a DIY project for this but then I found the Hot2O system in a box ( www.hot2o.com/How-FAFCO-Solar-Products-Work.html ). Prices start at $2,000 and it qualifies for a tax rebate.
I can enthusiastically recommend these, Here (in Australia) they are quite common and shown to pay back in a few years. As we are in a rural area and have easy access to fallen trees we run one in combination with a wood burning stove and heat exchanger which helps to boost the solar during winter. The combination is almost 100% effective (we have turned on the electric boost for about 2 hours in 2 years).
As a secondary consideration the wood stove can boil the water in the tank so it has to be vented (not at water pressure). However our tank has a large coil of copper pipe through it which acts as a heat exchanger. Thus the hot water is at the same pressure as the cold. This system works very well (i was originally worried it might reduce the heat available).
Highly recommended
For the record, I'm in the business, solar thermal manufacturing. Great comments. Regarding
cost (s) k, natural gas is still very inexpesive in many areas. Here in Florida it's $1.00 a therm. Large users such as state government, military, large industrial users, have even a lower costs. Very difficult for solar to compete on purly ecomonis terms. This is changing rapidly in many areas. There are enviormental issues with gas. As to Northern climate cost, look around. Lower cost systems are avaiable.
Solar heating is like an ideal DIY project, because it is so simple. I built a battery that has about one square meter surface using mostly scrap parts. Some stuff I had to buy totaled in at about 20$. Still need to hook it up though...
I guess best use for it would be a summer cottage or heating a small tub (some of them come with a pump that could circulate water in the battery and make it more efficient than with plain convection) - something like that, a place that doesn't need all year around hot water. Just make sure that your pipes wont't burst i the winter.
I grew up spending lots of time on boats. My parents had a "Solar Shower" that was essentially a plastic water bag with one side black and one side clear. It had a hose/nozzle on the bottom and a hanging loop on the top. We'd lay it out on the deck of the boat or on the dock and it would very hot. Hang it up and you've got a hot shower in a bag. Very smart.
I've been working with bamboo lately and I think I might build an outdoor shower with it in my backyard. Leave the bag out to heat in the day, shower with it at night. Very beachy!
i am finishing up a rehab of a 2 story rowhome in philly. i have radiant panels (not in floor) tied into a hotwater boiler. i plan to ge ta solar hot water heater, which would tie into the radiant heating as well. Are there sites that compare models and manufacturers so that i can figure out what is best for my needs. I dream of being able to get all my water heated without gas.
thanks,tony from philly
You guys have to look around more on the web. There is a new resurgence in solar hot water heaters here in Florida. I got a 40 gallon thermosiphon from siliconsolar . com shipped to me for $995 + shipping. Had the plumber install it and whammo free hot water. I also had it tied into my existing HW heater for extra capacity and emergency heating if I use it all for some reason.
I get free solar hot water panels from people who don't want to bother with them anymore. I am an HVAC contractor.
There is no way you can talk them into keeping them so I just pull them off the roof.
My vacation home is in the high desert and I now have 14 hot water solar panels and 4-120 gallon solar hot water tanks. That gives me 480 gallons of hot water plus I have a 280 gallon tank buried in the ground for additional hot water storage.
On sunny days even when the temperature is below 0 I can get enough heat to heat all my water and heat my 1500 square foot home. Since I have 760 gallons of hot water in storage I can go for 3-4 days before the water temperature drops below 80.
Cost to me was next to nothing. Just some labor to pull the panels off and then hook them up.
All homes should be built with south facing shed roofs and loaded with solar water heating panels in sunnier climates. Only chronically cloudy ares should be exempt.
But there are new tubes out there that work with ultraviolet and will work on cloudy days. We need to work on this technology and make it work.