High Mass Solar Storage

Larry C_13

Using the same idea, some antebellum houses used a ring of gas jets at the top of a cupola to create a draft to pull in cooler air thru the first floor windows to cool of the house.

Larry C

Justin Topel

High Mass Solar Storage

Has anyone had any experience with high mass solar storage? I have read about this a few times, but I was wondering if anyone on the wall has tried this yet. I am thinking of placing a significant amount of sand in a hole that is at a depth that will mantain the constant temperature of the earth and running pex throughout to store all the excess collected BTUs from solar panels. This could be done during the summer months and then used again during the winter. I hate to see those panels not running during the summer when the highest energy collection potential is best. I would of course insulate around the top, bottom, and perimeter of the mass. What are your thoughts on this? Have you seen this work before? Thanks for the imput.

Mr. T

Unknown

I am not aware of any study, experiment, or backyard mad scientist who has ever made this appear worthwhile.

scott markle_2

There is solar district heating system in canada that uses ground storage.

Sand is not a good medium, people mistakenly assume because it it dence that it make a good thermal storage medium, but because of it's structure it does not conduct heat well and conduction is crucial.

Think about how hot the sand at the beach is, but dig down a bit and it's a lot cooler. I assume it has to do with all of the air in between the particles

Drakes landing project

http://www.dlsc.ca/borehole.htm

Justin Topel

Very Interesting

That was my next thought. Maybe I could build a block barrier and waterproof it. Then fill it with water and utilize a heat exchanger to transfer BTUs to the mass. I suppose that this is not too complicated to figure out. I feel that a good deal of panels is required, but it is manageable. And maybe some other panels could be used for solar cooling. I don’t know. Maybe I will have to try this on a small scale. Thanks for the info on the Drake Landing. It is very interesting.

Mister T

Mark Eatherton

Who you calling a backyard mad scientist? :-)

Guilty as charged.

I drilled a well in my back yard (shallow, 10- deep) and installed a copper heat exchanger. It worked fantastically for keeping my solar array cool (heat rejection) but could not build a bubble of heat due to shallow water migration ;-(

The Japanese have a seasonal energy storage system that uses the snowmelt system to collect solar energy during the summer and store it in the ground, then extract it out for snowmelting during the winter.

Roth has a new hybrid solar/GSHP system coming out soon that is being tested over in Germany.

I am going to be doing some horizontal boring at Hydronicahh and use it to store excess solar energy produced during the summer, and hopefully re-harvest it with GSHP during the winter. If nothing else, I end up with a good GSHP system that will use copper heat exchangers for earth contact, and I have a great place to reject excess solar energy.

I think it obviously has some potential, but is dependent upon numerous variables (avoiding shallow moving aquifers for example) in order for it to be effective.

If you are going to use sand, be sure and throw some cement in there to bind all those air surrounded particles together :-)

ME

hot_rod

A good conductor

is the best way to move energy from the sun to the fluid and fluid to the heatload. That is why most solar collectors use copper as the absorber plate. It is also why the best radiant heat distribution systems are aluminum coated panels, or heavy extruded plates.

Dry sand is not a great conductor. Yes it's inexpensive and readily available.. Peeble bed storage was another concept tryed years ago with mixed results.

Water is by far a better place, than sand to store thermal energy. But it gets expensive in large, well insulated volumes.

There are some other mediums being tried, salts and other phase change materials. Google around for off peak storage systems that are being sold to take advantage of low off peak electric rates. The ones I have looked at are some sort of phase change material. www.steffes.com/offpeak/


In Europe they are experimenting with stratification and latent energy storage tanks, water with phase change materials. This Latento is one example.

www.solarnetix.com/index.php/Specialties/Solar-Storage/Latento-XXL-Hot-Water-Storage-System.html


The good news, if you want to get creative, is there are large capacity tanks out there for cheap. old LP tanks up to 1000 gallons are plentiful in LP areas. Insulated dairy tanks are available used. Some fiberglass tanks that can handle solar temperatures are available, even collapisable ones like this Haase. www.ichbin2.de
Finding the space and the insulation investment seems to always be the tripping point.

If sand is the final answer, consider adding some bags of portland cement to the mix It will bind it together and increase conductivity. Or order redimix concrete ready to go out of the truck, delivered and placed.

hr

Andrew Hagen_2

Solar Storage

Seasonal thermal storage has one huge problem. Thermal conductivity has units (btu*in)/(hr*ft^2*°F). Think in terms of the insulated boundary of your thermal storage. You can control everything about thermal conductivity except time. Seasonal storage has time against it. No matter how well you insulate the storage, it will lose a large amount of the stored thermal energy over the course of a season. As the storage time is increased, the efficiency of the system decreases.

Solar thermal has to be designed to take advantage of daily patterns of sunlight and energy use. It is for this reason that solar domestic hot water is a much better investment than solar space heating.

So what it comes down to is that best taking advantage of solar thermal energy for space heating, you must size the array for a diurnal pattern of storage and use. The collectors store energy all day and the heating system uses it all night. Drainback systems are the best way to go when designing for a high solar fraction for space heating.

As mentioned before, sand is a poor storage medium, because it is essentially an insulator. Water is a good storage medium because it is inexpensive, and it allows the tank to take advantage of convection around the heat exchanger and the resulting stratification in the tank. With solid materials, you are relying completely on conduction.

UNUSEXFER

solar storage

Check out: arthaonline.com

Bob Gagnon plumbing and heating

1500 Gallon Tank

I have a 1500 gallon storage tank that I made out of a wooden box lined with heavy duty roll rubber roofing. It was very inexpensive. This does not give me seasonal storage, but it does provide many benefits. The heat in the tank may last a week or two, depending on conditions, and my large collector array never overheats. I harvest all the energy that is available, instead of having a dump zone. I have a smaller two hundred gallon tank that runs hotter for domestic, and the 1500 gallon tank pre-heats the domestic and provides low temperature radiant heat. I get 100% of my domestic and about 20% of my heating with this setup. I don't think that we need seasonal storage we just need a lot of collectors and storage to last a couple of weeks, through long periods of cloudy weather. I believe high mass thermal storage is the way to go.

Thanks, Bob Gagnon

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Mad Dog_2

Guilty as charged tooo...\"hang me\" with Eatherton

Couldn't ask for better company. When I get time and extra $$$ I will do some experimenting along these lines with the tubing I laid in my asphalt driveway although I got throughly bashed by some here as an ignorant mad scientist. That will be an interesting experiement when it goes. Mad Dog

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Unknown

I'm sorry you got bashed mad dog, but take heart; we've seen the hot water you can pull out of a driveway in the summer. it's significant. haven't metered it but at decent flow the water temps were something like 115 on a light overcast day in july... impressive stuff.

Bob Gagnon plumbing and heating

Driveway heat harvesting info

I have been waiting for that information. I must of missed the post. Could you tell us the pump and pipe size? How about the flow rates and delta tee's?

Thanks, Bob Gagnon

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Unknown

Gary would know best (HOUND him Bob!!) but like I said we haven't metered it, unfortunately. this is 3/4" pipe set up for snowmelting (6" to 9" o.c., high flow). I don't know the dT or actual BTU collection, but I can say there are BTUs to be had even in the absence of direct sunlight... bright overcast (UV) still imparts significant energy. Good stuff... that was middle of the summer though.

Right now I can't say whether it's economically feasible or not, but I can say it is certainly possible to harvest heat.

hot_rod

too much in the summer, not enough

in the winter month, with solar thermal. That's the bottom line when you start looking at solar thermal for heating.

1500 gallons stored at 180F and pulled down to 90F provides.

8.33 x 1500 X (180-90) = 1,124,500 BTU. If none slip away from you (impossible) you have about 10 hours of heat with a 100,000 BTU/ hr load. or 20 hours at a 50,000 load.

So it gets to be a huge storage problem to get solar heating fractions up there. I did see some Swiss projects with a huge SF in the 90% range. Here is the tank required for a very small home. The entire roof was covered with solar themal panels.

Even with 15,000 gallons, and enough panel square footage to cover near design loads, they still have pellet boiler backup. I'd guess a system like this in the $50,000.00 range? Maybe much more.

I think realistically that 20- 30% solar fraction is sellable, beyond that the numbers are stacked against you.

Cover DHW loads, and hope for chillers to provide summer time AC from the same panels, would be a good target.
Unless money is no object.

hr

Bob Gagnon plumbing and heating

I was hoping

Mad Dog would respond. It may not work everywhere, but what about a water park or an ice skating rink, or a building with a heated pool, where they have a large summertime heat load.

Thanks, Bob Gagnon

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scott markle_2

That tank looks like close to $50,000! 50k buys a lot of natural gas even in switzerland! I wonder how the drakes landing project is actually performing, when I read about this a year ago many of the houses were not yet occupied.
Seems like the economies of scale in a district heating system could shift the economics favorably.

Unfortunately we currently have a glut of oversized houses built with little concern for efficiency or quality. There is little hope for converting the nightmare of ill considered development that is dragging down our financial system to anything even remotely alternative. Hard enough to even find people that can afford mortgages on this junk. Supplemental solar DHW could make a difference but with the way things are right now, how many families struggling to pay mortgages or worrying about job security can afford solar, even when it's sweetened by tax incentives.

Solar for the rich will do nothing for our collective security, who want's to deal with the limitations that solar orientation and design place on architecture. If the view happens to be to the north just heat the glass! Sorry Mark.

Justin Topel

Good Point Hot Rod

I know that you will definitely have great losses and it is very expensive to try and heat the entire house, especially the sizes they are built to today. But I am thinking of using a poured concrete tank with waterproofing. My father-in-law has designed those for nuclear plant water storage. They have lasted 25 years so far and still are working as planned. Thermal expansion does seem to take a toll on them, but these tanks are above ground. I was also thinking of possibly using pool collectors during the summer months to help assist in the heat production. I ran a quick report through RetScreen to see how the numbers might play out without the pool collectors. Based on the design I would receive around 75 million BTUs a year. That of course is not really taking in consideration the amount of losses that are imminent with this system. I did place some losses in the system and heat exchanger, but this could really help supplement a system if you were using low temperature heating. The key word is supplement. I am just trying to think of things in a different light. Payback may be a while, but can we name one thing that we have bought that has paid us back? Not too many things if any. We never purchase a car looking at the payback or even a boiler for that manner except maybe in the case of an upgrade. I try to sell my systems to people by using other terms besides payback. Yes they will payback at some point, but that is not the only reason for considering the installation. I am currently working with a company on a storage device that will have a long life span without leaks. I will keep you guys posted on the results. I also recently serviced some panels on a house that used them to supplement their heating. They had seven collectors on the roof which wouldn’t seem to do too much. The guy had the drainback system installed twenty years or so ago and ran the water through fan coil in his furnace. He claimed that he hardly ever had to use his back-up heat sources. His storage was around 440 gallons. The system worked all of those years without having any service done. He was pleased with his micro heating bills. I would be too. I know that the lab numbers don’t always seem to look to good, and then I find someone who is way under what I am thinking and their system is performing above the numbers. This industry is always exciting and offers constant learning and discovery. I thank God that I am in the middle of it.

Mister T

Derheatmeister

Google: Ute's in Japan

That will give more information on this subject

Justin Topel

Thanks for the article...

This seems very similar to the Drake Landing development. The article stated a payback of 10-20 years. If they were to install boilers for the same project, there would be no long term payback. It is just cheaper up front. As we know utilizing these types of technologies will reduce our need for fossil fuels and will possible lower the costs by supply and demand principles. It seems a win-win situation all the way around. We will be imparting work into so many others things besides oil exploration. Why not give jobs to the engineers, designers, drafters, surveyors, highway crews, drilling companies, tubing companies, grouting, solar panel producers, installers, electricians, pump manufacturers, and so many others that will benefit from this instead of just mainly oil companies. I know they have a lot of workers as well, yet the ones who seem to really be profiting in most situations is oil companies exec who are payed more in one quarterly bonus than we will ever make in a lifetime. I am not against them making money, but I feel that we could be placing it more effectively in the hands of many other people as well. Oh Boy……Now I am probably going to be labeled a socialist! That is not what I am for by any means, I am just trying to help by working with other people to find ways in which we can all help each other during these economic times. We can all help promote a different way of thinking. Just like what happened during the era where boilers were installed by Mongo Boiler Works and circulators that were sized by the Zeus Circulator Company. Sorry if any of you worked for them, I am just making a silly point not trying to attack you. We can start with a small change and have it go a long way. I am looking forward to the challenge! Thanks again for the helpful information.

Mister T

hot_rod

an unglazed, uninsulated collector

like a driveway or sidewalk will have a limited use. Probably fine in summer months maybe 100-120F supply at best?? But winter performance will be nil.

It would somewhat compareable to a swimming pool mat type collector. Here is a performance curve for that type of collector.

At the very left side of the graph at O on the bottom left corner, this indicates the collector and water return temperature at the same temperature,.

Say for instance 80F ambient and 80F return from the pool. At that condition the collector is nearly 90% efficient. Moving to the right, along the bottom shows a 10F degree drops in ambient. As you can see the performance of an unglazed collector drops quickly as ambient drops. At 50F ambient that collector performance is all but done. Without glass or insulation it losses are too great.

This graph clearly shows how powerful the evacuated air space is as in insulated, compared to unglazed and single pane flat panels. Hense the superior high temperature application of evac tubes.

So driveway collectors with the tube at the bottom of the pour or asphalt would see a temperature of ??, doubtful much over 100F So even in the summer months you won't collect or store much high grade heat. How much heating would you do with a thousand, or pick a number, gallons of 100F water? If in fact you could maintain it at 100F until heating season came around.

Maybe for some summertime pool contribution, DHW preheating, but fairly limited winter time use, with those expectd temperatures.

If you are doing your own driveway and have pex to spare for free or cheap, why not. But running the numbers shows it would be a fairly low grade, expensive collector to sell customers.

The cost of insulating, tubing, and connecting a driveway solar collector could buy a whole bunch of high performance glazed or evac tube collectors, that will soon be able to AC your home with absorbition chillers, also.

hr

Derheatmeister

Well said

By thinking this way we can a least "offset" some of the Energy needed for the world's "Requirement's"

I have been labeled all kinds of different way's in the past ( socialist, or being a fan of Dictatorships) just for mentioning things like " Yearly Mandated Combustion test" with the possibly of the system being redtagged or even shut down..
I still do not understand why some got there panties in a bunchkin over this and yet freely accept and mandated yearly Automotive emissions test (Grumpy old dogs do not learn new Tricks)

You just keep up the positive attitude, Richard :-)

Mark Eatherton

Japanese UTES link

http://intraweb.stockton.edu/eyos/energy_studies/content/docs/proceedings/IWAMO.PDF

Steven Eayrs

anyone here hear of this guy??

A guy, Bob LeFevre who owns a company named R Philips Technologies. Built a house in NH in 2001, and has yet to use anything besides pasive solar (85% of the heat), and active solar (15% of the heat using evac tubes). Guess its a 4300sq.ft. house, 15,000 storage under it. Was trying to make is to a seminar he was teaching at recently, but couldn't find the time.
Is it for real??? I think he has a web site under R.Philips technologies. Lots!!! of insulation.

Wayco Wayne_2

Passive solar

is the way to go if you can. I've worked several jobs recently where the heating was supplemented by active solar in a radiant floor. I am going to finish a job in a couple of weeks in a straw bale Passive design house. The main component being the south facing window shining on the slab that is the thermal flywheel at the heart of the house. This stuff is awesome. Smart too. My neighbors think I'm a mad scientist too. With radiant floors, snow melts sidealk, mod con boilers and now 90 evac tubes on the roof, I expect to wake up some day with a shock of white hair striping my head. :O WW

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Jamie Hall

my father-in-law

one Norman B. Saunders, who has passed away, was designing 100% solar houses in the late 70s and 70s in New England. And they worked, too -- I've been in a number of them. They weren't quite passive -- they had big (but very low velocity so quiet) fans which moved air from the collectors -- roof and south facing rooms with glass walls -- to the storage; usually lots of water. The best of them, in Shrewsbury, MA, would carry quite happily through a week of cloudy miserable winter weather.

They were super-insulated, but they also had heat exchangers to provide a minimum of 1 outside air change per hour for the house, to avoid air quality issues.

My recollection is about 5 to 10 percent more expensive than conventional, and most of that was in the insulation. Biggest problem was getting the contractors to do it right...

hot_rod

a few Canadian companies with air collectors

on the market. this is another simple way to harness solar, perhaps more controllable than large glass passive systems.

www.solarwall
www.enerconcepts

Justin Topel

Thats great!!

Thats great when the neighbors question your sanity Wayne. I have the same problem. I am just try and re-inforce their ideals by wearing aluminum foil on my head. Try it next time you go to visit. I can assure you of one thing...they will never forget you

Mister T

Royboy

I've worked on a couple systems

which were "high mass solar storage." Both designed by Bob Ramlow of Artha Sustainable Living in Amherst, WI. His book: "Solar Water Heating: A Comprehensive Guide to Solar Water and Space Heating Systems" gives some detail about these systems. They generally involve a couple foot insulated sand bed under a slab floor with PEX tubing delivering solar heat to the bottom of the sand bed. The idea is storage massive enough for some degree of seasonal lag, so late summer solar heat can help out during the heating season.

Both the systems I worked on have had some problems. The first I inherited midstream from a solar installer who went out of business and the collector array has had air problems that are yet to be resolved so no good test winters yet. Second house which I did the entire install has been used as a seasonal residence which really is not well suited to the system. The whole mass cools off when the house is unoccupied and then when they warm it up for winter use, the mass is working against you.

So I really haven't had a chance to evaluate these systems but I know Bob lives with one and has been involved installing dozens that he says perform well. My gut sense is that though part of what he like about them is the simplicity, it might be more effective to complicate them some by thermally separating the slab delivery from the storage bed and having a controlled heat delivery from storage rather than the passive & uncontrolled heat delivery in the way he does it.

I'd also note that I have intended to but have not yet done calculations to really look at the heat capacity of the sand bed and how it relates to the heat load and solar potential. Someday soon ... ;-)

I know of at least 2 systems that have been done with high-mass sand beds that were thermally isolated from the delivery slabs. One featured in Environmental Building News maybe a year and a half ago, one done by an outfit from Duluth MN. I'm heading tomorrow to Duluth for an Energy DEsign Conference where the installers of the latter system are doing a presentation. So I'll see if I can get some more info and post later in the week.

Roy

Sunrise Energy Services

Royboy

I've worked on a couple systems

which were "high mass solar storage." Both designed by Bob Ramlow of Artha Sustainable Living in Amherst, WI. His book: "Solar Water Heating: A Comprehensive Guide to Solar Water and Space Heating Systems" gives some detail about these systems. They generally involve a couple foot insulated sand bed under a slab floor with PEX tubing delivering solar heat to the bottom of the sand bed. The idea is storage massive enough for some degree of seasonal lag, so late summer solar heat can help out during the heating season.

Both the systems I worked on have had some problems. The first I inherited midstream from a solar installer who went out of business and the collector array has had air problems that are yet to be resolved so no good test winters yet. Second house which I did the entire install has been used as a seasonal residence which really is not well suited to the system. The whole mass cools off when the house is unoccupied and then when they warm it up for winter use, the mass is working against you.

So I really haven't had a chance to evaluate these systems but I know Bob lives with one and has been involved installing dozens that he says perform well. My gut sense is that though part of what he like about them is the simplicity, it might be more effective to complicate them some by thermally separating the slab delivery from the storage bed and having a controlled heat delivery from storage rather than the passive & uncontrolled heat delivery in the way he does it.

I'd also note that I have intended to but have not yet done calculations to really look at the heat capacity of the sand bed and how it relates to the heat load and solar potential. Someday soon ... ;-)

I know of at least 2 systems that have been done with high-mass sand beds that were thermally isolated from the delivery slabs. One featured in Environmental Building News maybe a year and a half ago, one done by an outfit from Duluth MN. I'm heading tomorrow to Duluth for an Energy Design Conference where the installers of the latter system are doing a presentation. So I'll see if I can get some more info and post later in the week.

Roy

Sunrise Energy Services

Bob Gagnon plumbing and heating

Moving and Storing Passive Energy

With my wood stove I simply recirculate all my radiant heating without taking any heat from my boiler or solar tank, and it moves and stores the heat from the wood stove room, into the other end of the house that is the coldest, wouldn't this work with passive energy too?

Thanks, Bob Gagnon

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scott markle_2

It's not passive if we \"move it\"

Bob,

Are saying is that you have a constant circulation radiant system that is helps move heat to cooler areas. Or do you have a more direct pick up for the heat from you wood stove? How effective do you feel this kind radiant heat spreading effect is? Have you tested your assumptions? I would think a small well placed computer fan might actually move heat for its relitive electrical consumption, Most wood stoves have heat shields that limit downward radiation, wood heat also tends to be very stratified, this might work a lot better with radiant ceilings than floors.

I believe the definition of a passive system is one in which energy flows are not forced by mechanical intervention. In a strictly passive system energy is directed but not pushed.

The term passive is also used for heating sources that are incidental, lighting, people, refrigeration etc.

"A New York Times December 26 2008 article No Furnaces but Heat Aplenty in ‘Passive Houses’ gives some welcome attention to this otherwise overlooked concept. While the article suffers from a poor description of how the heat exchanger functions and makes no mention of the existence of the smaller North American-style heat recovery ventilators, it does end with a great quote about keeping the house size to 500 square feet of floor area per person. Ultimately size is the key to sustainable housing." Elfstrom Engineering

http://www.nytimes.com/2008/12/27/world/europe/27house.html

Bob Gagnon plumbing and heating

It works Good Scott

The floor in front of the wood stove gets plenty hot, but I do have Radiant with aluminum plates in the walls and ceilings around the wood stove. This cools the wood stove room which can get too hot, and it heats the north side of the house which gets no passive solar either. It moves heat more efficiently and comfortably than air, think FHA VS Radiant Heat. I was hoping the recirculation would make the rooms more equal in temperature, and it did, what I didn't count on is that it also stores those extra BTU'S from the wood stove into the floors, walls, and ceilings in the cooler part of my house. When I get the house warm to the core this way, instead of just heating the air, the house stays warm for a lot longer. I think this same idea would work in a room that gets very warm from passive solar. Maybe we would have to say it is a passive/active hybrid?

Thanks, Bob Gagnon

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scrook_3

stove backing

Nice 'cuda.

What's the stuff sealing the fireplace opening?

Larry Weingarten

Jamie

Bill Shurcliff wrote a book "Super Solar Houses" about your father-in-law's designs. No doubt it could be found now by looking in the used book section of www.addall.com. That book helped me to figure out good control of the indoor space temperature by storing heat below and coolth overhead. Having LOTS of insulation and good air sealing make solar space heating possible. Too many contractors still don't appreciate it.

I seem to remember another Wallie was related to Mr. Shurcliff, who passed away not long ago. We, here on The Wall, get to carry forward and build on the work of some really extraordinary people. Thanks Dan!

Yours, Larry

Bob Gagnon plumbing and heating

Stove Backing

I used the high temperature insulation they sell at the wood stove stoe to seal the liner as it goes up the chimney, to stop the convection from sucking the stove heat up with it. It looks like pressed fiberglass with foil on bothe sides. Before I installed it I measured the temperature at the back of the fire box and it was about 250 degres. It is an outside chimney and I have maybe a foot of brick and no insulation, so I figured I was losing a lot of heat there, and also up the chimney around the liner and insulation. I'd estimate that I get 20% to 30% more heat into the room. At the same time I hooked up the direct air intake, for combustion, and I feel that gave me another 20% to 30%. On real cold nights the chimney would reverse when the fire died down, drafting lots of freezing cold air into the house, now it just goes outside. The house is a lot more comfortable with a lot less fires. And the Barracuda is 45" long.

Thanks, Bob Gagnon

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k_2

re

I was in a full solar house in southern NH about, damn, 20 years ago, more even and it was wild, very tall and thin with a huge concrete and stone core and he said he vented most of the time. Wonder if he still has that car....

Referencing hot rods example, pretty drafty house that would use 100k or even 50 for 24 hours straight......running a quick thought, 1000 gallons of oil a season, 180 day season, 80 percent net efficiency averages say 26k btus a day. So after a couple of days of no sun, yeah, it would get a might chilly.

One would think backup would be wise nonetheless

hot_rod

passive solar cooling

many of you know Dave Springer of Davis Energy in N Calif. Also a long time RPA member and BOD member. Quiet fellow very smart approchable engineer like Brad, Siggy and many others we know from these parts He also did early radiant and hydronic classes before the RPA was formed.

Years ago they designed the mechanical system for a visitor center at a park in S. Utah. A tall center, masonary circular room shaft allows warm air to rise and pulls cooler air in the bottom.

I had an article on that system, perhaps from an old Solar Today mag. I'll try to find it and post a link.

A lot of neat things can be done to heat and cool in the design of the structure. I think Dave is once again designing and providing unique solar systems and applications. He flies under the radar and you need to search out his designs dating back many years.

hr

Andrew Hagen_4

Options

I agree that high solar fractions for space heating are not economical at this point in time.

I have looked into it, and absorption chillers are extremely expensive for a residential application. My preference is to cover the DHW loads first, then as much space heating as the budget allows. The payback is really not there for solar space heating at this time (particularly in the Montana climate), so it is generally more of a feel-good thing than an economic thing anyway.

From a technical standpoint, I am more excited by MCHP than solar space heating right now. Imagine nearly eliminating electrical transmission losses. Unfortunately, our local utility has no net metering in place for MCHP right now and the spark spread is small so the payback is virtually nonexistent. I hope that will change soon, however these units are also still relatively expensive and have very limited availability. Obviously there are a few hurdles. Payback periods in the order of decades are difficult to swallow for those looking to save on their energy bills.

scott markle_2

Andrew, What does MCHP stand for?

Is this the honda generator that does waste heat recovery? As far as I'm concerned those systems should be excluded from Net metering because they will generate most of their "extra" electrical power at night, when there is no real need for it.

Why should the utility pay retail prices for off peak power generation that isn't needed? how does this promote change that has a collective benefit?

Andrew Hagen_4

Cogen

Micro Combined Heat and Power = MCHP

From a generation standpoint, I can see where it may create an excess of capacity during off peak hours. To be honest, I am not sure what the daily demand curve looks like in northern climates during the winter. I agree, these units probably make no sense at all in a warm climate. I have no say in how the utility balances the grid or determines what rate they pay. Some sort of net metering seems necessary to make these units practical.

The cogen units are appealing to me for a couple reasons. First, I like the idea of virtually eliminating line losses. Second I like the idea of a backup generator, particularly during winter months in remote areas when a power interruption can mean frozen pipes. I am not a huge fan of using natural gas to generate electricity, but the efficiency is so high that I think the net energy savings can be very positive. Obviously I have not worked out the details on these systems, but I am very intrigued by the idea.

If you have further insight into what I am not seeing or problems with what I do see, please let me know.