How solar air heaters work:
上图显示了太阳能空气加热器的基本概念，虽然有很多设计，但基本原理是相同的——一个小风扇将室内空气输送到一个朝南的壁挂式面板。空气在经过一个黑色表面后被加热，然后以更高的温度返回到被调节的空间。“免费”的被动式太阳能供暖，而且预算有限!
DIY太阳能空气加热器的视频在YouTube上大受欢迎，其中有几个主要的想法——回收易拉罐太阳能收集器、落水管太阳能收集器、屏幕或金属片太阳能收集器。如果你没有勇气自己制作，也可以在网上购买太阳能空气加热器，只要在网上搜索一下就可以了。
Aside from large commercial installations, the most common application for solar air heaters seems to be supplemental heat for individual rooms, like an addition, a workshop, garage or any other small outbuilding.
The reason we say 'supplemental' is that while while a modicum of heat can be collected on cloudy days, you're mostly going to feel the heat when the sun is shinning. And without some a sizable amount ofthermal mass to store heat and release heat, it's unlikely that anything but the mostwell-insulated buildingswill maintain a comfortable room temperature from sundown to sunup on a cold winter night.
If you're looking for a solar air heater to warm a building with no power, you can gain heat simply through natural convection as warm air rises, but you will get much more heat by forcing air through it with a fan. Fans don't require a lot of energy to operate, so a small dedicated PV panel would do the job when there is no other available power and will automatically drive the fan when air movement is needed most - when the sun is shining on the panel - and will stop at night when the panel cools down. 12v fans for desktop computer cooling are an ideal way to pressurise the system and get air moving for solar air heaters installed off-grid.
Pop-can solar panels:这简直太棒了，可能是唯一一个可以证明喝汽水的理由。然而，这是一个相当耗时的过程——罐头需要清洗，在底部开洞，去除标签，然后需要把它们粘在一起，最后涂成黑色。
Air is blown into a chamber at the bottom of the heating panel and forced up through the stacks of cans into a top chamber that collects the sun-heated air and directs it back indoors.
Downspout solar collectors:就像它听起来的那样，这个设计用涂成亚光黑色的标准屋檐槽落水管取代了太阳能空气加热板上的一堆易拉罐，以吸收太阳射线。同样的原理也适用于这种太阳能收集器，虽然你会在材料上花更多的钱，但你会节省很多劳动力，它看起来更整洁。最终的结果是一样的;当空气在阳光下通过黑管时，它会被加热。
Solar screen or sheet metal heat absorber:The designs we found involved 3 layers of screen to ensure a unified black surface. Screen collectors typically do not separate air into individual chambers like the previous two designs; air rises up a single chamber behind the screen or flat metal surface.
Of the two, it would seem to me the screen design sounds like a bit more work compared to using sheet metal (as seen above), which could be made using old metal roofing and painting it matt black. Labour aside, testing between a screen collector and a pop can collector showed that the screen collector did provide more heat,read more here.
How much heat can solar air heaters provide?
That depends on a lot of variables:
Solar Panel size:This will determine the volume of air you can condition and the output temperature. Choosing what size to build or buy will depend on your needs and how much exterior wall space you can dedicate to a panel.
Solar absorption:Panels are limited in how much heat they can collect depending on how reflective the black surface is, and you will do better with a matt paint than glossy. Glazing will instantly reflect about 10% on its own, but is essential especially in areas with air movement creating a wind chill factor in winter, so really the best you can hope for in overall performance from a solar air heating panel is about 80% absorption of available light.
Heat Panel Conductivity:Materials with higher conductivity will improve solar air heater performance. A black PVC pipe for example, would not provide as much heat as a black metal pipe. Even different metals will have different rates of conductivity. Copper is one of the better conductors but it is very expensive and can be tricky to get in larger diameter or to get paint to adhere to, so the advantage of increased conductivity would likely not be worth the added cost.
To choose the downspout panel option for a diy solar air heater panel build, be sure to use metal and not plastic, and if it has a glossy finish it would be worth it to paint it matt black.
Home performance:How much heat a house needs to keep occupants warm is determined by how much it loses. A solar heater will provide a greater percentage of the required heat in a home if that heat demand is lower, sohow well insulated and airtight a house iswill be a deciding factor on how big the passive solar air heatr needs to be to make a difference.
Cloud coverage:In areas that are regularly overcast, like Vancouver noth shore in Canada or Pescadero in California for example, it may not be worth the cost and hassle to either buy or build one. Certainly the payback period for labour and money invested in a solair air heating panel would be much longer.
Latitude:The further north you go the less sun hours you will have on a winter's day, so the cost or effort required to make a panel will stop being worthwhile at a certain higher latitude - although if the heat collecting panel is wall-mounted and extra heat might be welcome, then in northern areas it might still be worthwhile - any readers in the Northern Territories or Alaska who have built or used solar air heating panels are welcome to comment below!
The downsides of solar air heaters:
The Achilles heel of most renewable energy generators like solar air heaters is reliability, but also energy storage. The wind doesn't always blow and the sun doesn't always shine (or more accurately we can't always see it). So the main drawback of solar air heaters is that you only get heat when the sun is shining.
Short winter days and unpredictable cloud coverage make it difficult to rely on solar air heaters as a primary heat source because you will gain all your heat during sunny hours but then have to go an easy 16 hours at times with no heat input. And shorter days in winter means that they generate the least amount of heat when you need it most - though this can be mitigated by south facing wall mounting. In all but the most heavily insulated homes in more gentle climates, with thermal mass included for heat storage, you will likely need an additional heat source likehigh efficiency wood-burning stoves or fireplaces, or ifoff-grid an electric-free wood pellet stove.
Storing solar heat (thermal batteries):
If youincorporate thermal mass into a home to store and release heat, you can distribute the heat collected over a longer period of time, and there are any number of creative ways to do this. Sticking with the DIY theme for say - sheds, garages or greenhouses, you could run the heated air through tubes embedded in sand, bricks, masonry etc before venting it directly into the conditioned space. Rather than simply heating the air, dense materials will absorb some of that heat and slowly release it over time after the sun goes down.
There is nothing to say you couldn't do this to an addition on your home, it's just that we are generally a bit more picky with the final appearance in our houses. So a slightly more aesthetic design might be required in a house than in a workshop or garage to store some of the heat generated by a passive solar air heating system.
Specifically withgreenhouses built in cold climates, they have a tendency to overheat in the day but sometimes get too cool at night for young plants. Keep in mind that it is more important to keep the roots warm than the plant itself, assuming of course the air stays above zero. If you include a solar air heater in a greenhouse design and transfer some of the heat to a platform with thermal mass on which your soil boxes can sit, you could start a growing season earlier.
It's also a good idea to include a bypass vent of some kind in the solar air heating panel that can release air in summer to prevent overheating when the panel isn't actively in use - as "cooking" a panel .
You could also apply theprinciples of passive heating and coolingby placing the panel under the eave where it will have full exposure with the low winter sun but be shaded when the sun is high overhead and you have no need for heat.
How to build a DIY solar air heater:
Web searches reveal an endless list of designs and assembly techniques for DIY solar air heaters, the same holds true for DIY videos on YouTube. Different designs will resonate differently with different people, so pick the one that best suits your skill set, tool collection and attention span. If you come up with any brilliant design ideas or modifications for passive solar air heaters in the process, please share them in the comment section below.
Check out the DIY video below to give you a better idea of how easy solar air heating panels can be to build.
Passive solar air heating panels, whether bought or homemade, are an interesting way of saving energy, money & carbon footprint of homes with renewable energy.Find other articles & information onrenewable energy systemshere :
And to see more guide pages in the EcoHomeGreen Building Guides for Sustainable Buildings - Click Here |
I am currently helping someone to troubleshoot a solar air heater that did not perform very well during those cold winters in the Great Plains. When I look for real world information on actual performance results, the testing period is always in early spring, summer, or early fall. Do you know anyone who has rigorously tested their solar air heater in the dead of winter - you know, when folks really need some heat?
Hi Alan,
We actually should have some results soon, we built asolar air heated floor(Air heated panels feed air tubes in a concrete floor) and should have some results in the near future, so be sure to check back soon. As for trouble shooting in your particular case, if it was purchased then I'd check with the manufacturer or installer, but given that you are asking here I will pepper you with suggestions based on the assumption that it is a DIY job -
Maybe panels aren't getting full sun hours in the day due to shading
That's just a few ideas, let us know if it's homemade or not and what you've tested so far, it would be fun to troubleshoot this with you.
Really interesting system, thanks for the article.
我也做了一个和你的一样的太阳能加热器。在晚上，太阳没有出来，外面很冷，加热器似乎是反向工作的，它自己把热空气吸出房间，输出冷空气。How are other heaters hooked up to stop this from happening
Hi Mark,
如果你在太阳下山的时候运行它，它确实可以反向运行。我们无法提供如何安装的技术细节，但可以设置一个自动调温器，当进入空气的温度对你有利时，自动调温器就会打开或关闭。