solar heat collector

krisman

hello, i need help on a solar air collector. my furnace was installed about fifteen years ago and it is just now starting to give troube, so i thought instead of putting much more into it, it would be wise to invest in free heat. I just want to know anyones experience with solar heat because i dont know the first thing about these collectors. Someone please explain to me how to install, how they work, how much money, and how effecient these heaters are. I would say they are pretty much maintenance free and very frugal right?

Cariboocoot

Re: solar heat collector

Whoa!

Great idea, is solar thermal.
But replace your furnace with it? Probably not. You'd need to have a very well insulated house in an area where there's lots of bright, winter sun. Doable if you live in a relatively mild climate, but probably not if you're in the snow-belt. You could end up having to rebuild the entire house. Now how cheap is that furnace repair?

And most such installations are home-made.

For some interesting stuff and info along these lines, check out www.builditsolar.com

There's a lot to this sort of thing, including local regs governing installs, whether you use a liquid or air system, et cetera.

Another possibility would be a heat pump.

Sorry; it just isn't possible to give a short, simple answer like: "you do it like this and it costs this."

BB.

Re: solar heat collector

The following has been posted around here a few times for domestic hot water and/or home heating:

BB. wrote: »

If you want a do-it-yourself kit... This one appears to be hard to beat:

www.solarroofs.com

Solar Guppy has many years experience with a system from them and has been pretty happy. It does require proper maintenance to keep running well and to prevent problems (like freeze damage).

There have been a few threads here that link back to several extensive home projects--right down to installation photos, and documentation of mistakes and corrections...

Link 1
Link 2

Follow the off-forum links. The several projects/websites highlighted are very educational.

This is an interesting project for a solar heated shed and a control the guy now sells to support a pure DC off-grid solar heating system.

And this one is a bit more low tech home made heating system. Also very interesting and informative.

Between the two above links, they probably give the best detailed explanations of how to do a major home heating/domestic hot water project that I have seen.

The second one is, by itself, probably not practical for a city home system--but both give great ideas of the scope of such projects.

-Bill

krisman

Re: solar heat collector

and what exactly does a heat pump do? im not familiar with them. and could a solar collector be built for backup emergencies to keep warm? we dont have a lot of snow in tennessee

Cariboocoot

Re: solar heat collector

krisman wrote: »

and what exactly does a heat pump do? im not familiar with them. and could a solar collector be built for backup emergencies to keep warm? we dont have a lot of snow in tennessee

A heat pump is a commercial system which extracts heat from land or water to heat your house with. They are usually 'reversible' so that they can provide air conditioning as well. Expensive, but often a more efficient choice than separate furnace/AC install (in an area that will support it).

Problem with using solar heat for emergencies is that they really only work when the sun shines; storing solar thermal is a whole 'nother issue. You need a lot of well-insulated mass.

You need to take a holistic approach to this. Read up on the many options and see how they fit in with your needs and your location. The first thing to look in to would be conservation; it's nearly always the best value for your energy $.

BB.

Re: solar heat collector

A heat pump is just a refrigeration compressor... But setup so that it can either remove heat from inside the home and pump it outside (cold inside, hot outside). Or the refrigerant flow is reversed and the heat is dumped into the home and the cold air outside (heat inside, cold air colder outside).

It turns out that an Air conditioner "run in reverse" (i.e., heat pump set to heat the inside if the home) is more efficient at heating the home then running a simple electric resistance heater (down to about 32F/freezing or so)... Below freezing, alternate sources of heating (electric heater, oil, etc.) are usually needed to boost heating.

For example, in the Sanyo Mini-Split A/C thread--there is a heat pump option available for these small A/C units.

-Bill

krisman

Re: solar heat collector

i have taken many steps. energy effecient windows. opening curtains during the day, even cell shades that have a high rf value. what other ideas does anyone have to feel toasty in winter months?

has anyone ever thought of the old pop can solar collector trick? only sitting it inside a window and letting it vent warm air during the day, or something along these lines? would that be possible?

icarus

Re: solar heat collector

There are a million different strategies to use solar heat. Starting simply with direct solar gain from sun facing windows and ranging to exotic phase change salt solutions to store heat in active systems.

My suggestion is that before you do anything, you spend a lot of time reading and understanding what technologies are out there, how they work, what they cost etc. I would also suggest that you do EVERYTHING you can to conserve 1st. Dollars spend on reducing you loads will translate to a much smaller system cost, and fuel costs. You might also consider doing solar hot water 1st, as it is usually much more cost effective.

Depending on your location/climate etc good conservation can reduce your heating loads by 20% without trying real hard, simple passive direct gain (south facing sun porches etc) could reduce your heating load another 20% making a total gain of ~40%. These numbers are just arbitrary, but you get the point.

The biggest issue in my opinion is reducing heat loss so that you don't have to pay to reheat the air over and over again.

Good luck,

Tony

mikeo

Re: solar heat collector

what other ideas does anyone have to feel toasty in winter months?

Living where you do, if you have an unobstructed south facing exposure for your house, consider building a sun porch. Glass it in with single pane surplus glass door panels or older windows. Have some thermal mass like stone for flooring, add some black filled water barrels for mass. Have an insulated sliding glass door open to the inside of the house. When the porch is warmer then inside the house, open the sliding glass doors, when it is colder close it off. The sun porch will probably stay warmer then ambient temps when it is cold outside helping to keep the cold air from infiltrating inside. This also adds a nice living space outside your house in good weather. Some trees that drop their leaves in the winter may be need to keep the sun porch cooler in the summer.

BB.

Re: solar heat collector

Home Power Magazine is also a good place to read about conservation ideas too.

-Bill

krisman

Re: solar heat collector

i was kind of wondering about the eden pures too. i have an uncle that says he can heat his whole house with 2 of them. but i was just wondering if you just sat a fan by a register or by a window with sunlight, if that wouldnt do about the same thing? i was also considering something like this http://www.amazon.com/Eco-heater-602-High-Efficiency-Electric-Whole-Room/dp/B00185XISW/ref=sr_1_15?ie=UTF8&s=home-garden&qid=1258947497&sr=8-15
what do you think?

benthere

Re: solar heat collector

For what it's worth, I have 6% of my floor space in south glass and 7% of my floor space in a vented trombe wall. All this in a small concrete block house. The CMU walls are mostly empty but the trombe wall area is poured solid with concrete. I'm happy with the setup but still need my propane heater to put the finishing touch on.

The point of my post is to report the success of the trombe wall and the fact that I prefer it in unvented mode. If vented, the amount of heat discharged to the house is (theoretically) more, but the very enjoyable radiant heat in the evening is diminished. That radiant heat is going good by about 5pm and is tapering off by 10pm. It compliments the direct gain from the south glass very nicely.

icarus

Re: solar heat collector

Remember, heating anything is a simple equation of BTUs. The reality is efficiency comes in two ways, the first is how many BTU are lost from the building envelope from all sources. Greater insulation leads to fewer BTUs lost.

The second is how efficiently does any given heat source turn it's energy into BTU in the building envelope (or hot water if we are taking hot water). Wood fire places for example may actually have a negative efficiency, that is drawing more heat out of the building than it puts into it! A modern hi-ef wood stove might near 75%. Gas appliances can near 95%.

The link you provide is a simple resistance heater, and regardless of hype, heaters of this type can only deliver BTUs in relationship to watt/hours consumed. (3412 BTU/KWH) That rate is constant regardless of the design of a resistance electric heater. A better heater isn't more efficient per se, but it may retain heat better, or disperse heat better etc.

The only electric heat source that can be "more efficient" is a heat pump system. A heat pump, depending on medium can be even more than 100% efficient, putting more than 3412 BTUs per KWH into the building.

So, in short, remember watch for hype, use the best source of heat that you can, and use it efficiently.

Tony

BB.

Re: solar heat collector

The Amazon Eco-Heater Review is in this thread... Short answer is it boarders on both a scam and possibly dangerous.

Regarding IR Heaters--Assuming you don't heat the room or the whole home, but just point it at the person--it may be cheaper to operate than a standard electric space heater.

In general, a pure resistive electric heater tends to be one of the more expensive options for heating a home.

Insulation, double pane vinyl windows, window coverings, weather stripping, and other conservation measures tend to save you money over the long term.

The way the eden pures websites are laid out (at least the top couple of results that I clicked in Google), the selling of Insulating Paint Filler from NASA ("SuperTherm" comments in this thread), and such---I would stay well away from the whole thing. At best, you may end up paying 2-4x as much over a "cheap" electric heater from a local store.

-Bill

Cariboocoot

Re: solar heat collector

I doubt that linked-to heater is worth the money. Critically examine the blurb: "Similar to a central heating system, yet far less expensive" How do they figure a space heater i similar to central heating? Other than providing heat, there's not much similarity at all. Another part says: "heats an entire room using the same amount of electricity as four 100-watt light bulbs". Okay, so it's a 400 Watt heater. That's not much, even for a 10 x 12 room.

For electric space heaters, your best choice is the oil-filled radiator type. They usually have switches which allow you to select three different Wattages, plus a thermostat.

But in terms of net outright heating, electricity is a lousy way to heat anything. It's just not efficient. And to reiterate Tony & Bill's sentiment, if your losing btu's through the 'envelope' no source of heat can be efficient.

mike95490

Re: solar heat collector

Lets not forget the miraculous "Amish Mantle" electric fireplace !

icarus

Re: solar heat collector

Snake oil burns well too!


Infra-red or radiant, watts is watts= BTUs is BTUs. There is no magic potion.

The one way that resistance electric heat makes sense is for small zone heating were other options might be too big, such as bath rooms. Or a ceramic heater under your desk so that you can keep warm, while keeping the rest of the house cooler.

Given a choice, a number of small Rinnai heaters heating specific zones or areas would be what I would choose.

Tony

Dave Angelini

Re: solar heat collector

krisman wrote: »

i have taken many steps. energy effecient windows. opening curtains during the day, even cell shades that have a high rf value. what other ideas does anyone have to feel toasty in winter months?

has anyone ever thought of the old pop can solar collector trick? only sitting it inside a window and letting it vent warm air during the day, or something along these lines? would that be possible?

Where do you live? Location is everything this time of year!

mike95490

Re: solar heat collector

krisman wrote: »

hello, i need help on a solar air collector. my furnace was installed about fifteen years ago and it is just now starting to give troube, so i thought instead of putting much more into it, it would be wise to invest in free heat.

Most areas, an installed furnace, is a code compliance item. You won't be able to sell or possibly transfer your house without one.

There are some good, efficient furnaces, and after your furnace is working, you can look into the solar options. Also depends on your winters, if you don't have much sun in the winter, you can't get much heat from it. Cloudy area or Clear ?

icarus

Re: solar heat collector

Actually Mike, that is not quite correct.

The last code book (UBC) I used, (and it has been a few since I needed one!) stated that dwelling units needed to be "able" to provide heat of ~65f (if memory serves) 30" off the floor. It does not mandate how it do so. There is no reason that a house have central heat or a furnace system. Zone heaters (gas or electric) are perfectly acceptable to meet the letter and spirit of the UBC. There is some debate on the efficacy (and acceptance) of portable heater. From a practical as well as safety issue, portable electric heaters should only be used as temporary devices due to basic safety issues. Most portable gas appliances are unvented and therefore NOT permitted, even though they are commonly available. (Not recommended either!)

Tony

mike95490

Re: solar heat collector

If a furnace is installed, and then removed, or disabled, it will take a LOT of little heaters to make up for it, costing as much or more, than repairing the central one.

krisman

Re: solar heat collector

ok mine is an outdoor gas furnace. i know they say gas is natural but i just cant believe that, it gives me a headache. anyway tell me more about this heat pump deal, what does it take to install one? do you install it inside or out? and would you have to take the furnace out and put it in place of the furnace or would it just be beside the furnace?

I have been thinking a lot about this, if there was some kind of sheeting or something to put over the windows to magnify the sunlight something like 2, 3, 4x. like a magnifying glass, wouldnt that heat the inside considerably?

and the pop can option. if it got a good day of sunlight, about how long would it stay hot after the sun went down?

niel

Re: solar heat collector

krisman wrote: »

ok mine is an outdoor gas furnace. i know they say gas is natural but i just cant believe that, it gives me a headache. anyway tell me more about this heat pump deal, what does it take to install one? do you install it inside or out? and would you have to take the furnace out and put it in place of the furnace or would it just be beside the furnace?

I have been thinking a lot about this, if there was some kind of sheeting or something to put over the windows to magnify the sunlight something like 2, 3, 4x. like a magnifying glass, wouldnt that heat the inside considerably?

and the pop can option. if it got a good day of sunlight, about how long would it stay hot after the sun went down?

think of a heat pump as a large air conditioning unit able to be thrown into reverse. usually part of it is inside and part of it is outside. you should do a internet search to educate yourself on them before jumping into it or making any conclusions about it.

if you were to magnify the sunlight entering your window this will not add more heat to your home, but would concentrate what is there already and the result would be a fire.

most collectors of heat will dissipate that heat to cooler surroundings nearly as fast as it is collected depending on ambient temperatures unless a provision is made to preserve it like insulation.

icarus

Re: solar heat collector

If it were as easy as "magnifying sun coming through a window" we wouldn't have an energy problem.

It is all a simple matter of BTUs. Figure the heating load of the house in BTUs, reduce the losses as much as possible, add in the possible solar gain BTUs. There is no magic bullet.

As to a heat pump: http://en.wikipedia.org/wiki/Heat_pump

Tony

GreenPowerManiac

Re: solar heat collector

I guess painting the house all black would do the trick, however I wouldn't want to be near you in the summer time when you get the cooling bill.


Solar "Black" water collectors are the most common heat absorption these days. A simple pump pushes the heated fluid through a heat exchanger inside a water tank. Then pump the heated water through a thermostatically controlled radiator of some sort. Instructables.com had a segment on a home-made solar collector for 5 bucks. You'll love it when the sun is out and hate it when not. I only use my radiant floor system when the sun is out, and switch over to forced air LP gas when not.

I can't wait until an Absorption Chiller hits the market for Solar water heating & a heat pump to create air conditioning.

RCinFLA

Re: solar heat collector

To put things in perspective.

A gallon of fuel oil is worth about 140,000 btu's of heat.

One square meter of full sun for an hour is worth about 3,400 btu's of heat.

This does not take into account solar collector efficiency loss.

On a first pass, look up how many gallons of fuel you use then calculate how much solar area would be needed to match the btu's consumed. Then pray for sunny days.

LucMan

Re: solar heat collector

Check out this site http://www.gotohallowell.com/. The Acadia will work down below zero degrees, I bet that you don't get too many days that cold. You may be able to connect to your existing ductwork without to many modifications.
Tennesee is a great area of the country for heat pumps!
A heat pump moves heat from one area to another. In winter it moves heat from outdoors to the interior of the house, in summer it moves heat from the inside of the house to outside while removing humidity.
Heat pumps can give you 3 units of heat for every unit of power that they consume at 47 degrees outdoor temp. Up to $1500 Tax credits available for energystar rated equipment.

krisman wrote: »

and what exactly does a heat pump do? im not familiar with them. and could a solar collector be built for backup emergencies to keep warm? we dont have a lot of snow in tennessee

furnacecompare

Hallowell had a very exciting cold weather heat pump called the Acadia that they sold from 2005 - 2011.  Unfortunately, their equipment had a number of technical problems, and they went out of business in 2011, leaving thousands of customers with no guidance for how to maintain their heat pumps.  If you're having a problem finding a contractor to work on your unit, or you're wondering what went wrong, check out this list of resources.