Using PV Panels for Shading Structures

I've added a small new section on using PV modules that both generate electricity and provide shading.

The main entry is an article sent in by Amy and Dennis Heidner which describes in good detail how they went about designing and building a deck canopy that provides shading for the deck and for the living space in the house behind the deck.

Shading structure using PV panels.

One of their concerns was that it would be too dark under shading surface made with PV panels.  They describe how they were able to take light meter readings behind a variety of PV modules and find a module that had enough open area to provide the lighting the wanted.  They also included small glazed areas above and below the PV modules that also let in light.  In the end, they got just the light level they were looking for.

Incorporating small glazed areas to get the right light level below the canopy.

The new PV module shading section also includes the use of bifacial PV modules for shading.  Bifacial PV modules accept light from either side and do not have the opaque layer behind the silicon cells that regular PV panels have -- this means that they are semi-transparent and this works out well for some shading situations.

There are also links to a variety of projects that use PV modules for shading just to show some of the unusual and creative ways people have come cup with.


All the details on PV modules for shading structures...

A shade umbrella using PV panels

Gary

How Large a Solar Collector Do You Need to Heat Your Hot Tub?

This is a pretty good method to determine how large a solar collector is needed to heat your hot tub. 

The size of the collector needed to heat a hot tub depends on a lot of things: volume of the tub, how well its insulated, how good the cover is, what your climate is like, how hot you keep it, ...   Its not easy to take all that into account to get a good idea what size collector you need.  But, I ran across the method detailed below in "More Other Homes and Garbage" that uses the temperature drop of the hot tub over 24 hours to determine the daily heat loss for your hot tub in your climate and for the way you use it -- it seems like a good approach to me.

All the details here...

By the way  "More Other Homes and Garbage" is a terrific book written the 80's, but full of good ideas, good analysis, and written in a style that won't put you asleep -- and, its only $8 used!  Better get one before they all disappear!


Given that hot tubs are the biggest energy users in most homes that have them, its not a bad idea to do the test on your hot tub to see how the heat loss looks, and even if you can't do a solar heater, things like more insulation and a good cover can make a lot of difference.


Gary

Night Air Thermal Mass Cooling Using Water Barrels

This is a scheme that I am experimenting with to cool my shop.  It basically blows cool night time air over a collection of 50 gallon barrels filled with water to store "coolth" in the water. 

The idea is to cool the barrels down during the night hours, and then use the stored "coolth" in the barrels for space cooling during the daytime.  This requires a climate in which the night temperatures drop down to low levels even though the daytime highs are uncomfortably warm -- this is true for much of the western US.

While I am using the scheme in my shop, it could be used to cool any interior space.  Note that we use a variation on this cooling scheme to cool our house ...  The basic question is: does it make sense to use a fan forced flow of cool night air over thermal mass to store "coolth" for later use in daytime cooling?

Logger plot of water barrel storage and shop temperatures
with fan forced outside air flow over barrels at night.

This is definitely a work in progress, and I'm looking for any ideas people might have to make it work better.  I think that it has the promise to deliver good cooling performance for near negligible energy consumption (SEER 150 ish).   


This scheme only works for climates in which the night time temperature drop to relatively low levels even when the day temperatures are hot -- typical of a lot of the US west.


All the details and questions on night air cooling of water barrel thermal mass...

Water barrels for storing night time "coolth"

Rough prototype cooling tunnel to direct fan forced night time
airflow over the water barrels for good heat transfer.

In this particular scheme, the same water barrels are used to both store heat in the winter and store "coolth" in the summer!

Gary

Don's Solar Scooter -- 8 years and still going strong

Don just sent the 2012 update for his solar electric scooter -- see below.

For those who missed this nice and simple conversion of EVT 4000E electric scooter into a solar powered electric scooter, the full plans and how-to are here...

Don's conversion is somewhat unique in that he added folding PV panels to the scooter so that it can charge while he is at work or in town.

Don and the solar scooter

This is the 2012 update from Don:

The scooter still flying...returned to Earth Day 2012 At University of Michigan, Flint.    Scooter a hit again.  Kind of humbling that the interest is still strong.  Will be on the local TV 25 news in May.  They are doing an ECO Fuel Story about people doing things to avoid purchasing gasoline. 

The scooter survived another winter outside.  I took off the  rear view mirrors and covered Scooter with plastic except for the solar panels this year.

14 miles into Flint for Earth Day and 14 back.  No problems.  The evening before I replaced one of the top cross locking bars that was bent the night before Earth Day last year when Scooter tipped over in the wind when I was out of town and a storm hit.   I had hand straightened it, but decided to replace it this year.  Replacement took less time than going to town to purchase a new piece of stock. 

For others with electric scooters, check you tire pressure.  On the first after winter  trip to town a couple of weeks ago, the light kept going to the second or third level down from full charge indicating a higher amp drain.  This despite a full battery.   Apparently only having 10 lbs of pressure in tires made for 40 lbs,  does effect performance and subsequently range.

That is about all for this years update.
Don


See the link above to see the details on converting the scooter to solar and 8 years worth of riding experience with it.

Showing the solar panels folded out for charging.

Thanks again to Don for sharing the details on doing the conversion and the updates on how its working out.

Gary

Sandbed Heat Storage for Solar Homes -- A Minnesota Example

An example of a home in northern MN that uses an insulated  sand bed under the home to store solar heat for  space heating the home.

The house is 600 sf and has a 2 ft deep sandbed under the concrete floor slab.  The home is well insulated with strawbale walls and R60 ceilings.

About 160 sf of conventional solar thermal collectors add heat to the sandbed on sunny days.

The heat from the sandbed is conducted directly into the living space through the floor slab.

After 3 years in the house, the owners are very happy with the house both from an energy saving and comfort point of view.

All the details on this Minnesota sandbed storage solar home...

Thanks very much to Maureen for providing the details.

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Also,  revamped the whole section on sandbed storage homes and related ideas....

Gary

Doug's Solar Projects

For those of you who don't know about Doug Kalmer, he is a renewable energy expert who lives in Tennessee, and who really walks the talk on the renewable energy and sustainable living fronts.

His projects use simple, elegant, well thought out designs that are durable and cost effective.  Most of the projects can be built by any reasonably skilled DIYer.

The projects cover an amazing range of renewable energy and sustainable living areas.

Note that Doug's house is going to be on the solar tour this year, so if you live in the area, go have a look.

Here is a list of Doug's projects on Build-It-Solar -- follow the links for full details:

Passive Solar Home... 

Doug's 1985 solar passive home in Tennessee has been largely heating itself through several decades.

It uses a combination of passive solar gain for heat and earth berming to reduce heat loss.

Backup heat is provided by the masonry heater described below.

4.6 KW Grid-Tied PV System...

This is Doug's latest project.  It is a 4.6 KW grid-tied PV system that uses Enphase micro inverters on each PV module to make utility compatible solar electricity.  The mount system is all Doug designed and built and is simple, strong, durable and very cost effective.

Masonry Stove...

Doug designed and built this efficient and very beautiful masonry stove to provide backup space heating for the passive solar home.

The masonry stove is designed to burn hot, fast, and clean while capturing the heat in the stone and radiating heat for hours after the fire goes out.

Solar Greenhouse...

The attached solar greenhouse was built for and amazing $300 using sliding glass door panels.

The solar greenhouse allows plants to be started in January and February and then moved out.  The greenhouse also provides some heat to the house.

Efficient Thermal Shades...

These thermal shades provide R values equivalent to the best of the commercial thermal shades and also look very nice -- all for about $15 a shade!

They use the Reflectix as the insulating material.

In my climate, this thermal shade can pay for itself in a single season over a double glazed window.

Closed Loop, PV pumped Solar Water Heater...

Thermosyphon Solar Water Heater...

Doug has two solar water heating systems.  

Both are simple and cost effective designs that work well.

The closed loop system heats water for his house.

The thermosyphon system heats water for the shop/studio.

Slipform Walls...

Doug used slipform walls for his home, and this project explains how to build slipform walls.

This is a technique that owner builders can use to provide a wall that is very durable, cost effective to build, and looks beautiful.

Hot Water, Cold Beer...

This is an interesting project that uses a salvaged AC unit and "Corny Kegs" to make an efficient heat pump for cooling the beer keg.

The heat pump takes heat from the beer and uses it to heat domestic water.

Directory of Doug's projects...

I want to thank Doug again for doing these projects and for taking the time to document them and make them available  -- Thanks!

Gary

Simple Solar Bird Bath Heater

This is Jim's nice simple solar bird bath heater that keeps the  bird bath water unfrozen during the daytime in cold PA winters.

The finished birdbath with collector panel facing right.

This shows the internal construction -- its a passive thermosyphon solar collector that circulates the solar heated air across the bottom of the metal bird bath container.

All the details on Jim's solar birdbath...

More on solar heating water for animals of all sizes...

Gary

An Exceptional Video on Climate Change

Even though Climate Change is one of the main reasons for starting Build-It-Solar, I don't say much about it because talking about it seems to turn a lot of people off, and it seems more effective just to provide a lot of projects that both help on the Climate Change front and save money.

But, I thought that this video by Jim Hansen was exceptional in that it gives a simple and sensible statement of the Climate Change problem, AND it proposes a solution that might be acceptable to a much wider audience.

Have a look -- its only 17 minutes: http://www.ted.com/talks/james_hansen_why_i_must_speak_out_about_climate_change.html

If you want to leave a comment on the video, that's great, but comments that are not constructive and thoughtful will be removed.

Gary

Time In a Can -- Pinhole Solargraphy

Kevin has sent in the details for a really interesting project that combines pinhole photography and seasonal solar paths through the sky.  This would make a really nice school project for learning about both pinhole photography and understanding the path of the sun across the sky through the seasons.

A couple month Solargraphy "photo"

The project uses a pinhole camera made from an aluminium can to capture images of the suns path through the sky for an extended period.  The picture just above shows an example for 54 days.

Pinhole camera operation

The pinhole camera captures an image on photographic paper.  Kevin gives all the details on how to get the pinhole size right and how to set up the photographic paper in the can.

Putting the pinhole in the aluminum can.

Once the camera is done, you mount it outdoors with a view of the southern sky and wait.

A Solargraphy camera setup outside.

All the details on how-to on Solargraphy...


Gary March 8, 2012

An Under the Radar Plug and Play Grid-Tie PV System

Ken has done a very interesting grid-tie PV system.   Its a system that just about anyone can do for a few hundred dollars.  Basically, using Ken's scheme, its possible to do a grid-tie system at less than $2 per peak watt.

Two things make the the low cost possible:

- The use of a low cost China import grid-tie inverter.

- The glut of low low cost PV modules on the market right now.

The inverter comes in at about $0.35 a peak watt, and PV modules can can had in the $1 per peak watt area (plus some expensive shipping).   With some homemade mounts and a few odds and ends it will probably all come in under $2 per watt.  The recent US average for commercially installed grid-tie systems in the US is $6.80 per watt (from Solar Today) -- so, this is a substantial saving.

Ken's 500 watt PV system

The only real fly in the ointment is that the inverter is not UL approved for grid-tied operation.  But, it does have the anti-island feature, so it shuts down automatically if the utility grid goes down.  This is basically a bootleg system.

Even though the system is simple, there is some know-how involved in putting it together correctly, but Ken's blog entry goes through all this.

The Ningbo Sun 600G -- other sizes available.

Of course, you won't get net-metering with this system, so if the system is producing more power than your house is using at a given time, you won't get credit for the power that goes out to the grid.  But, with a small system like this, that won't happen very often.

So, if you want to save a few bucks on your electric bill and a half a ton of CO2 emissions, this offers a way to do it.  

All the details on Ken's system on his blog...

Ken is, of course, aware of the bootleg nature of this system, and is interested in hearing what people think of the whole idea -- pro and con.  Probably best to leave comments on Ken's blog to keep everything in one place.


There are some commercial systems in the works that may offer a way to buy these kind of plug and play systems down at the local Home Depot with all the approvals  -- some listed here...

If the low budget and significant saving are appealing, but you are hesitant about the whole bootleg thing, bear in mind that there are a lot of small solar heating projects that come in well under $0.10 per peak watt :)


Gary