Hi
Normally on knots, I’m about to close down and pack up my workshop, and demolish and rebuild both the shop and our adjacent house. So it’s housebuilding for the next 12 months!
I’m guessing I’ll be here a bit – am interested in:
- solar heat
- high insulation standards
- innovation in the interests of a sustainable house
First question: I’ve just come across the Chinese Evacuated Glass Tube Solar Water Heater technology, and it looks exciting. Is it being used in the US, and where would I go on-line for an up to date heads-up?
Malcolm
Replies
Oh, and I should have said - I'm in New Zealand!
Malcolm
Malcolm,
The evacuated tube, solar water heaters are available in the US, many manufacturers. I don't have any first hand experience with them. They run at the higher end, as far as initial cost. This page has some good info and many links. There are Federal and some state tax incentives in the US for installing alternative energy sources. These can help with recovering the costs of the system. There may be something similar in NZ.
http://www.wbdg.org/design/swheating.php
Beat it to fit / Paint it to match
I know this is of little relevance to a New Zealander, but I'm going to stick it in anyway just in case you are up in the mountains. The evacuated tube solar water heaters are so efficient that they will not melt off snow that falls on them. If it snows, they stop working until the snow falls off or blows off or whatever. The panel type will melt themselves clear much quicker.
Ron
Thanks
We don't get much snow (only get about 10-12in of rain each year where I live) but it can get pretty cold in winter.
The more I learn about this technology the more I like it. The question now is, what sort of backup do I need!
Malcolmhttp://www.macpherson.co.nz
Malcolm,
In my area a typical solar water heating setup using flat plate collectors circulating anti-freeze solution heats an insulated tank of about 40 gal. capacity through a heat exchanger. This tank is used as the infeed for a tank type hot water heater. The solar is an add-on to the kind of system which is found everywhere. It doesn't replace anything - except the fuel for the second tank.
One word of advice which was offered to me very emphatically: "Get the good pump!"
Ron
Yes, thanks
I'm looking for a system that could, at a push, completely replace conventional hot water systems. Until recently, solar options (here, anyway) were too expensive.
Now, with cheap EGT systems that work on cloudy days and in freezing weather, it seems that it might be possible to engineer a household heating system that's 95% independent.
That's what I'm looking for!
Malcolmhttp://www.macpherson.co.nz
Malcolm,
You'll need some storage capacity. How do you go about figuring how much?
Ron
"Assuming you have calculated the heat loss from your house, you can then compute the heat loss per degree of temperature difference.
Q = heat loss rate(in btu/hr) / inside temp-outside temp = X Btu/hr-Fº
Next, choose the maximum continuous time period you would expect to be without sun. For illustration purposes, we will design for a three-day period.
S (3-day) = 24Q (degree-days for 3 days)
This is the amount of energy we must store.
Volume = total storage requirement divided by the product of density, specific heat, and temperature difference.
If we assume that the maximum water storage temperature will be 150º F, and the minimum useful temperature is 80º F, the effective temperature difference is 70º F. For water, density is 62.4lbm/cu ft, specific heat is 1.0 Btu/lbm-Fº. Since there are 7.48 gallons in each cubic foot, we require a storage tank for 1775 gallons (237 cu ft x 7.48). Calculations for rocks or other storage materials follow a similar procedure."
He, he, he... if you read this far, it's from Other Homes and Garbage, p 125-6. ISBN 0-87156-141-7 A great reference for us non-engineers which also includes heat loss calculations for common building materials. The tank for my next house is 600 gallons, primarily to heat the indoor pool. Slightly over-sized, but it was only $75 with 1/2" steel walls (high pressure tank). Nobody else wanted to bother moving it. Gets mated with 450 sq ft of flat plate collector, also recycled.PAHS Designer/Builder- Bury it!
What else is in that book, man? I want one.
Ron
LOL...
For those of us who also can hardly make a computer go, it's great. Really is an engineering manual for non-engineers. Included are chapters on house design, small-scale electricity generation, solar heating, waste-handling systems, water supply, agriculture and aquaculture, and a whole lot of tables of useful info. Subtitle below "Other Homes and Garbage" is "Designs for Self-sufficient Living".
Mine's from 1975 and is well-worn. Being that old, some of it's obsolete. Certainly all the system pricing is, but that's of little import. Before there was an internet it was crucial for me to design what I have here. Now, it's still easier to grab it than do a search, like for your question here. I did heat loss calculations on our place and discovered I was over-insulating my exterior walls. Majority of my heat loss was through my non-leaky low e windows. Surprised me. But being that old, there's no correction for a high mass house in designing a heating/cooling system.
Or for instance, I can grab it and quickly compare heating climates in the US. Unfortunately doesn't cover Nova Scotia. Does compare insolation for various latitudes. Or help me design my compost pile to give me the best compostition for my required nitrogen, phoshoric acid, or potash levels. Complete with N and C/N ratios for various wastes, animal and plant. Need U value for glass block? It's there.
You get the idea. Now, get the book. Published by the Sierra Club, founded in 1892 by John Muir. IIRC, someone once told me there was a second publication, O H & G II or some such. Looks like $5-8 delivered to your door.
http://www.abebooks.com/servlet/SearchResults?sts=t&y=9&kn=other+homes+and+garbage&x=21
Happy reading.PAHS Designer/Builder- Bury it!
someone once told me there was a second publication, O H & G II
Yes, there is a second version of the OHG book.
Ok, so where's the review?PAHS Designer/Builder- Bury it!
Didn't buy it. Just saw it advertised.
A job I am doing has just had one installed....Solar Hart. It should be functioning in a about 3 weeks. I can let you know how well it works then it you like.
I dont know where all the Solar Hart components are made.....but I would avoid anything made in China like the plague. Pay the money and get a quality unit, you wont regret it.
As for backup.....I wouldnt rely on the thing alone. You have to have some sort of backup. ( A little paranoia be a good thing )
I would prefer a wetback on a woodburner for that, but then.....I like woodburners and dislike electric.
Not an exponent of the DILLIGAF system.
Edited 6/18/2006 8:36 am ET by AJinNZ
Thanks, much appreciated
Do I have your email address? Can't remember whether we 'talked' on another topic earlier in the year or last year.
I suspect that whoever retails these in NZ is getting the tubes from China, but will check that. There are a number of Chinese makers ramping-up fast, and producing these things by the millions of units - I think the technology is well proven, but will look for independent advice on that as well.
Very interested in how you get on
Cheers
Malcolmhttp://www.macpherson.co.nz
Yup, we did converse a little while ago.
You can email me via this thing if you cant find my addy.
I have an alternative energy/houses book or 2, can email you the details if you want. Very useful info on whole house stuff that can make a huge difference if your building from scratch.
The solar tube technology IS well proven, however I would still stay away from chinese if I could. I dont care how much a 'maker' insists that thier product is made to strict standards, quality control etc etc......it never is. Quality slips and the customer ends up wearing it.
Not an exponent of the DILLIGAF system.
Thanks
Found your address!
Malcolmhttp://www.macpherson.co.nz
If you want mega insulation......straw bale. Eco friendly and cheap material. I believe there is an outfit down your way that specialises in them.
My next house is gonna be straw. Woodburner based hotwater, solar electric for lights etc and diesel generator backup ( already got the generator ) and if I get the right bit of land.......micro hydro unit.
The minute I dont need to be connected to the grid, I will leave it. Rising power costs and the unstable supply we have at the moment means payback time is quite short.
An alternative energy expo that is held every year in Christchurch has an outfit that sells complete solar setups. I asked how much for a system that would power a typical house...............18 to 20K. For a couple like us that doesnt run 10 appliances and every light all at once, be way less than that.
Not an exponent of the DILLIGAF system.
$20K seems too low. I think MiSo spent $31k on the panels alone. I will find out exact costs today.
gk
> choose the maximum continuous time period you would expect to be without sun <
EGT works with or without sun - that's the key breakthrough! Just need daylight.
Malcolmhttp://www.macpherson.co.nz
Yeah, I saw that. Gonna be a little difference in performance. Principle still applies. Amory Lovins also showed you can also get solar gain with a S. facing window (in your locale), but it won't be much.
Other Homes and Garbage is hardly cutting edge anymore, simply very useful. Including answering your question.PAHS Designer/Builder- Bury it!
if you read this far, it's from Other Homes and Garbage
One great book ain't it, Tom? Got my copy in late 70's or early 80's. Put me in touch with energy and human comfort.
> You'll need some storage capacity. How do you go about figuring how much? >
Don't know, that's one of the things I'm hoping to discover from someone who has a working system. We've been talking about this today, and are considering solar plus on-demand gas as our total system. If we can heat and store enough water, we can think about relying wholly on solar.
We only need backup in the bathroom (a 100% reliable shower) and the kitchen - 2 small gas units might suffice. Thinking!
Again - the key is EGT's ability to generate heat in all daylight hours, regardless of cloud cover or outside temperature.
Malcolmhttp://www.macpherson.co.nz
> They run at the higher end, as far as initial cost <
Which is interesting, because the local (Chinese) costs are very low - like $US130 for an entry-level setup, up to $2.5k for the top end. That's very cheap. When incorporated in a new build (as opposed to retro-fitting) with a minimal backup system, this is potentially cheaper than a conventional electricity-heated system.
Malcolmhttp://www.macpherson.co.nz
take a look here for more info. the chap posts on breaktime (but i can't remember his name) so you should be able get loads of info.http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
I have a great idea for solar efficiency. There should be 12" square panels made of glass with a vacuum in between. The sunlight would pass thru the glass and heat up objects (Water tubes or thermal mass) and the vacuum would stop any heat from radiating back out. The multiple panels wound be able to make any size or can be laid in layers.
Sungod,A vacuum won't stop heat from "radiating out." It only stops conductive/convective losses at center of your hypothetical panel. Edge effects will be large with small panels.Our sun radiates its energy to us through 93,000,000 miles of mostly vacuum.Bill
I can provide some information on evacuated tube systems. I have installed one (actually two connected into one) The system I installed was provided by a german company called Viessmann. In the link I provided to them you will find both the exposed tube model and the enclosed panel model. Apparently the exposed tube model is more efficient and effective partially due to the fact that the tubes may be rotated to better match the sun angle of your site. The link to MisoHouse or MiSo* will take you to the project that I was a part of. If you like to dig then the MiSo* site will provide alot of answers on solar design. The project incorporates hundreds of thousands of dollars in research and is still unfinished as I am currently involved in planting the thing in it's final location in Ann Arbor, Michigan. I also included a PDF of the MiSo* Mechanical Estimate which may help you to plan how best to use such a system. FYI...We supplemented the Viessmann system with a small (5 gal.) electric hot water heater.
gk
http://www.misohouse.org
http://www.viessmann-us.com/web/canada/ca_publish.nsf/Content/SolarSysteme_ca_english
Here is a bunch of pictures of the Viesmann System installed on the house. BTW...when I installed these, I knew absolutely nothing about how they worked (all of the onsite manuals were in german) I was brought into the project as a "ringer" being an architectre student and competent carpenter/remodeler. So, unfortunately, the upper array of tubes is installed upside down and doesn't work. It was a snap decision matter of me saying "hey, I can plumb it anyway you's guys want...this way is quickest, easiest, and looks way cooler." I will know next time...which will be in a month when I reinstall the sucker.
Thanks again!
I'll chase up the internet links tonight. I'm thinking about buying and trialling an entry-level setup. Rebuild here will be in 2 stages - demolish and rebuild workshop first, then demolish and rebuild the 1950's house (while 'camping' in a 15 year old semi-independent extension - it's really 2 houses side by side).
Thought I might set up a temp system on the new workshop as a test-bed.
Malcolmhttp://www.macpherson.co.nz
If you live back in the woods and aesthetics aren't an issue then there are cheap and fairly efficient ways to make DIY solar water heaters. The system we used costs 2000.00BPD or about $3700.00 retail. As A research initiative and non-profit org. the wholesaler cut us a deal and we got our systems for about $5000.00 for the pair.
FYI: If you are serious about green building then keep in touch. As a recent University of Michigan Alumni, and lead carpenter to the MiSo* project, I currently have a great deal of informational sources at my disposal. Not the least of which is a friendship with a professor whose Phd is in Environmental Sciences and who is a genius in sustainability. Furthermore if you are interested, I would love to explain some of the other systems used in the MiSo* house.
GK
Thanks again - we'll keep in touch!
Am intending to build 'green' - well, to the extent that we will be building to very high insulation standards, with the intention of being as independent of the national grid as possible.
The goal is a house we can 'heat with a candle', through extreme insulation and solar gain. I'd like a hot water/solar radiator system, and hot water for kitchen and bathroom use also heated by solar. We'll probably use gas for cooking, and the hot water backup will be 1 or 2 small on-demand gas heaters. We think! It's still all on paper - going to talk to the builder Weds!
We've talked about tilt-slab concrete with cast-in insulation, but may end up framing in timber, cladding with corrugated zinc, and packing in the insulation. We'll probably pour a new concrete pad on top of the existing pad, again with cast-in insulation.
Joinery will be a challenge - I like the new American vinyl, but think it will be expensive here.
And no - we don't live in the woods. Sort of in town. here's the viewhttp://people.cohums.ohio-state.edu/macpherson10/home.jpg
Malcolm
http://www.macpherson.co.nz
Edited 6/19/2006 8:54 am ET by Malcolm
A great and affordable wall system is made by Insulspan (http://www.insulspan.com) which is located in Michigan and has two Canadian locations. It is your basic Structural Insulated Panel System (SIPS) and is also made by others.
gk