Over/Around Window Solar Air Heating Collector -- Help!

 

The
Mother Earth News
folks have a strong interest in a solar air heating collector that works in conjunction with a regular window.  This is based on the long term popularity of the "Heat Grabber" collector that MEN published a number of years back.
While the Heat Grabber has been popular and works well, it does suffer a bit from limited collection area and, also because it sticks out from the building, which does not fit some situations.  So, the MEN folks are interested in anyone's ideas on how to improve the design.

 

The link below is my rough first prototype effort at a solar air heating collector that could be installed over a regular window.
The idea is to use the existing window to get air into and out of the collector.  This avoids any need to cut holes in the wall for vents.  It also makes it feasible to just install the collector over the winter.  Some design "challenges" remain.

So, have a look, and if you have any ideas to improve this design or have an alternative design, please leave a comment, or email them in.

Details on the prototype over/around window collector...

The first cut prototype over/around window collector.

The air ducting and screen absorber for prototype collector.


Gary

3 Ways to Save Energy That are a Bit "Out There"

Here are three areas where significant energy might be saved in a home with fairly simple systems.  One has to do with using some of the heat in the hot air up in your attic, and the other two have to do with recovering some of the heat we waste in showering.

Regular showers are a major waste of energy.  Typically we spend about 3 KWH heating water for a shower, and then send about 85% of that energy right down the drain.  It amounts to about 300 KWH for a family of 4 per month.

Using The Heat In Your Attic
This page looks at some of the ways that all that heat up in the attic might be used productively.  This includes recovering heat for domestic water heating, space heating, pool heating, and cloths dryer air preheat. 
Some of these look fairly practical (to me).

I've been logging the temperatures up in my attic for about 6 months and the plot of these temps is included.  We live in a very cold climate, and it still looks like there is some potential.

Details here...

Recovering Heat From Shower Water Drain Pipes
This page looks at all the energy we send down the drain when taking a shower, and in some of the ways that are currently out there to recover some of that energy. 
It considers one (as far as I know) new method, which is basically to rearrange the drain plumbing to retain the shower water in the homes heated envelope long enough to recover the heat in the water for space heating. 
Some ways of doing this, the resulting energy saving, and a small test to examine the potential of this method are discussed.

It may seem like there is not really much potential here, but for heating climates, the potential energy saving for a family might be of the order of 1200 KWH a year.

Details ...


A Very Energy (and Water) Efficient Shower Design
This is a look at a shower design that was looked at for potential use on very long range commercial jet airplanes.  It is a very efficient design both from a water use and energy point of view.  It may not be for everyone, but have a look.

Details...

So, I'm particularly interested in whether you think any of these ideas have some merit and are worth pursuing (or not). 
Or, maybe you have some of your own "Out There" ideas you would like to share?

UPDATE: Turns out Kenneth has built and uses a recirculating shower... 
Kenneth's interest were more in getting long showers with very high flow (6 shower heads) without breaking the bank on energy use.  Its a nice simple design.

Note that Kenneth has also done a very nice Solar Shed project that does both solar space and water heating -- hope to have the details on this up soon.
Thanks Kenneth!

Gary

New Content on Build-It-Solar

Pop Can Collector From Sweden



A very nicely done aluminum pop/beer can collector.  Lots of attention to detail, and lots of good assembly pictures.  In Swedish, but the pictures plus Google translator make it quite readable.
Pop can solar air heating collectors force room air through connected columns of black painted aluminum soda cans.  The sun heats the pop cans and the heat is transferred to the air.  The even distribution of airflow and large heat transfer area should make them efficient collectors.
Details here...

Update on Chad's Solar Heating System
Chad has made a number of changes to his solar water and space heating system.  He has also logged and measured the performance of the system.

All the details and performance graphs...

Efficient Inflation System for Double Skin Poly Greenhouses
Many
poly skinned greenhouses use two layers of poly with a small blower
inflating the space between the layers.  This gives you cheap double
glazing, and reduces heat loss.
Most of blowers are set up to run 24/7,
but this article shows a way to cut down the run time dramatically using a
small pressure switch and a very simple check valve.  With the check
valve, the blower runs only when enough air leaks out to the point of
needing reinflation.

Details here...



Facebook Page
I've put up a page for Build-It-Solar on Facebook. 
Basically I have no clue how this all works, so if you have any ideas for the Facebook page, please let me know.

We just broke 500 fans today, so have to be doing something right :)

Massachusetts Zero Energy Challenge Winning Home

This is a very impressive less than zero energy home.  It uses a
combination of reasonable size, excellent thermal envelope, very
efficient appliances, some passive and some active solar heating, and a
PV driven mini-split heat pump for additional heat and cooling.

The end result is a true zero energy house that can be built within a reasonable budget.

I cover a few of the highlights below, but all the details on the house are in the article here...

Performance
The monthly performance chart below speaks for itself.  For the year 2009, the house produced significantly more energy than it used.


Highlights
Double stud, R42 walls insulated with cellulose insulation.
R100 cellulose attic insulation.
Triple glazed R5 windows with R7 interior thermal shutters.
Very good infiltration sealing.
Emphasis on south windows for solar passive gain.
Concrete slab floors for heat storage thermal mass.
Solar water heating
Solar air heating collector to for additional space heating.
Exceptionally efficient appliances and lighting.
Heat recovery ventilation system.
Efficient mini-split heat pump for heating and AC.
4.9 KW grid-tied PV array supplies all electrical power and then some.

Double stud R42 cellulose insulated walls

Total cost of the house without land is $180,000.

Altogether, and exceptional house.

Thanks very much to Doug and Tina for providing this material.

Gary

Spring Solar Projects

Solar Hot Water

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Now is a good time to study up on, and start building a solar water heating
system, so you can get it in this summer.
There are several high quality DIY designs that cab be built for inside of $1000. 

 Many solar water heating
downloads
 




Solar Greenhouse or Sunspace

 A place to grow some plants, produce some free heat for the house next winter,
or just a nice place to sit and have a cup of coffee with the newspaper. 

 Many Solar Greenhouses and
SunSpaces  -- ranging from $20 to $200,000.

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Passive and Low Power Cooling

 Here are many ways to keep your house cool, and at the same time save money
and reduce Greenhouse Gas Emissions.  Shading, whole house fans, landscaping, earthtubes, insulation and sealing, reflective and garden roofs, ...
Lots of ideas here.
 Passive (and
efficient active) Cooling






Solar Pool and Hot Tub Heating
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 Solar pool heating is arguably the shortest payback solar technology.  
Take the chill off the pool, and be easy on the planet at the same time. 

 Solar pool heating
information
My favorite quote on solar pool heating from Tom Lane in the Home Power Article Pool Heating Article:
 "Three gallons of oil refined and burned provides 400,000BTU ... Once.
Three gallons of oil, made into a 4 by 12 foot solar collector, can provide
over 10 million BTUs per year ... year after year"


How about a Summer Outdoor Solar Shower?

This is a very simple solar project to get started with.  It can save energy and reuse shower water for plant watering while providing a nice outdoor shower experience!

How to build info for several outdoor solar showers...






Build Your Own Solar Electric System

Solar electric systems have become much easier to self install over the years.  If you are careful about the safety issues, and have done some home wiring, you may want to give this a try.  Plan it this spring, and build it this summer.

Details on my self installed system...

More on DIY PV...



Do a Water Conservation Project

Spring is a great time to get started on an outside water conservation project.
Dozens of projects described in detail here -- rainwater harvesting, greywater reuse,
rain water gardens, ...

All the details on water conservation projects...


Any other ideas --- make a suggestion.

Gary

Some New Stuff

This is just a collection of some interesting (at least to me) items added tot he site over the last week or so....

Harvesting Fresh Water From Fog
Areas with regular daily fogs (e.g. some coastal areas) can harvest impressive amounts of fresh water from the fog.  Nets catch the fog and then channel droplets from the fog into a catch basin. 



Details...

Booklet on "Hot Water From Your Woodstove"
This is a good 45 page booklet from Lehman's describing a couple systems for adding a heat exchanger coil to the firebox in your woodstove to heat water.  Good detail on both thermosyphon and pumped systems, and lots of information on troubleshooting and doing the installation safetly.




Details...




Skysails -- Kites for Towing Ships
These are large kites that can be deployed under favorable wind conditions to reduce fuel consumption.  With favorable winds, fuel consumption can be reduced as much as 50%.
Operation of the Skysails is largely automatic.




Details...



Homes From Cylindrical Grain Storage Bins
A collection of links to homes made from cylindrical steel grain bins.  These homes offer a thermally efficient shape, and some options for good insulation thickness -- plus and interesting look.

Details...









Gary

UAZ Students Help Local Businesses to Reduce Energy and Water Consumption

I thought this was a great program to
get students involved with renewable energy and also help local businesses with
energy and water costs. 

Students from the UAZ Free Enterprise team identified two local Tucson businesses in need of some help on energy and water use, and then worked out and implemented a program to help the businesses reduce energy use, water use, and carbon emissions.

Here are the details on what the team
did -- there is contact information at the end if you want information on
starting a similar program ...

I have to brag a little here and mention that my granddaughter Kelly was one of the team members :)

Gary

Zero Energy Homes for the Rest of Us

While visiting St George Utah recently, we found that we were in
town during the parade of homes, so we looked at a few of them.  One of the
display homes was a very efficient home built by Sun-Savvy Inc.  I was very
impressed by this home and the other homes they offer.

Their design combines a very good and very tight thermal envelope, heat
recovery ventilation, passive solar, solar thermal and PV arrays, and efficient
mini-split heat pumps to make a home that should be able to achieve net zero
energy use in the southern Utah climate.  The display home has a LEED
Platinum rating. 

Even more impressive to me is that these are very nice and very "normal"
looking homes.  These homes appear to be very easy for the homeowner to live with. 
While the energy efficiency does add some cost, the homes appear to be cost
competitive with ordinary construction homes.  In other words, these are
net zero or near net zero energy homes which should have a very wide appeal to
ordinary home buyers -- you don't have to be an eco-freak (like me) to like
these homes. 

We took the full tour, got a lot of pictures -- all the details here...

Much more on solar homes here...

Clerestory windows -- great daylighting.  These open automatically when a set temperature is exceeded.


The energy recovery ventilation unit -- an earthtube is used to precondition the intake air to the ventilator.

It seems like a lot of the "net zero" energy homes you see are a long ways
out of the mainstream -- they tend to be architecturally unique (some would say
strange) and come with an acre of PV panels that would add $100K+ to the cost of
the house were it not for some very very generous (and perhaps questionable)
rebate programs.  I don't see this type of near zero energy home ever
catching on and becoming widespread.  On the other hand, a design like the
Sun-Savvy homes seems like it could have very wide appeal.  I hope it turns into a trend.

Gary

Our New Grid-Tied PV System -- First Sun

The new PV system we have been working on putting in is up and running.  There are many pages of detail and a hundred or so pictures that go through the whole planning, design and installation process in mind numbing detail here...
Sections on performance and economics of the system are also included.




The system is a 2150 watt grid-tied system.  It uses the new micro-inverter approach from Enpahse -- so, each PV panel gets its own small grid-tie inverter.

The panels are ground mounted with our own mounting racks. 

We did the whole installation ourselves, and I've tried to include enough detail to be helpful to anyone who wants to install a PV system of their own.  I've tried to cover not only the details of the component installs and wiring, but also the stuff like deciding on what kind of system, locating the panels, doing a solar site survey, and going through the permiting and net metering process.  It should be enough reading to put you to sleep for a week of nights.



It was a technically interesting and fun project -- not having any previous experience with solar electric stuff, I learned a lot. 
But, the economics are also interesting.  Basically, the system cost was right near $10K or $4.65 a watt -- after rebates this gets down to $6.5K and $3 per watt.  Better than what I was expecting.  The $ saving per year if you pay 10cents a KWH would be $300, or about a 5% return on the $6,500 -- tax free and energy price inflation protected.
Not so bad, but when you compare our PV to well thought out conservation/efficiency projects, or to DIY solar heating projects its comes out a very very distant 2nd -- some examples in the Economics section.

I've fallen behind in getting other projects that people have sent in up, but now that the PV is done, I plan to catch up right after Thanksgiving -- so, keep the projects coming in!

Gary

Energy Fairs

This is the season for a lot of the annual energy fairs, so check around and see if there is a good one to go to in your area.

The fairs are a great way to learn about renewable energy projects, go to workshops, meet some renewable energy people in your area, and find some deals.

I keep a list of all the Energy Fairs I know about here...

If you know of others that are not on the list, please let me know...

Gary

Home Build PV Panels and System

In this new article, Hans describes in detail the solar electric (PV) system he built from the solar cells up.  The system includes 3 homemade PV panels, as well as the balance of system components to make a full functioning solar electric system. 

Full description of the PV system ...


Hans maintains a web site that provides more information on the project as well as other renewable energy projects.

Gary

An Exceptional Residential Energy Retrofit

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Gordon and Sue took a drafty 1963
brick schoolhouse with almost no insulation and converted into a home that
could meet Passive House Institute standards, and that has a heating bill that
is 6% of a similar size code built home in their area.   Building a
new home with a thermal envelope this efficient would be an excellent
accomplishment -- doing this in a retrofit situation with all the challenges
that go with trying to bend an existing structure to your needs makes it much
more difficult.   Meeting nearly all of the space heating needs with
a good thermal envelope and passive solar heating was a very difficult
challenge in this tough 7,150 heating degree day climate in Ontario.  On
top of all this, the house looks normal and fits into its neighborhood just
fine.

Full details...





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This is the most carefully thought
out and carefully executed energy retrofit I have seen.  

Some of the features of the retrofit include:
R40 Larsen Truss walls, triple glazed R6 super windows, glazing revamped for
passive solar heating, a new solarium, a hand crafted masonry heater, and much
more.  In addition to a very good thermal envelope, Gordon gives a lot of
attention to fire safety and to redundancy in the space heating system. 
Like most good designs,

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this
one is simple and robust without a lot of gadgetry.



Gordon has done a very good job of describing the logic leading up to the key decisions on the insulating, glazing, passive solar, and thermal mass solutions used in the final design.  He has also described some of he things that did not go so well, and why -- all good information for would-be rettrofitters.

 

The
full details include a 30 page description of the design and construction
process, an extensive photo gallery covering all stages of the project, and a
very detailed thermal analysis spreadsheet.  

 Gary

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Window Condensation Calculator

Insulating shutters or window treatments that fit inside the window are a very cost effective way to reduce heat loss from windows.  We have a section on insulating window treatments that provides a raft of ways to do this.  I got an email from Dave in the UK pointing out that these kinds of insulating window treatments can also cause condensation on the inside window surface, and that this can be a problem.

I gave Dave some kind of vague and not very helpful answer on humid vs dry climates and the like.  Dave, being more of an engineer than me, was not satisfied with generalities, and came up with this very nice Window Condensation Calculator that can be used to predict exactly how much of an insulating treatment you can add before getting condensation -- yea Dave!

An insulating treatment installed on the inside of a window increases the likelihood of condensation forming on the window because the added insulating value of the treatment lowers the window surface temperature.  If the window surface temperature is lowered enough, it goes below the dew point of the room air, and condensation begins to form.  The lower the window surface temperature and the looser the window treatment fits, the more condensation you will get. 

There are basically two ways to address the problem:

1. Use a window treatment that fits snugly enough that very little air circulates between the window surface and the insulating treatment.
   
   
2. Choose a window treatment with an R value low enough that the window surface will not go below the room air dew point.  

Dave's calculator tells you what  the highest R value window treatment you can use and still avoid condensation on a loose fitting thermal shade -- very nice!
Dave's condensation calculator is based on Wolfgang's Dewpoint Calculator -- also very handy.

It turns out that this critical R value depend on:

• The room temperature and relative humidity
  
• The outside temperature
• The R values of the existing window and the insulating window treatment.

The room temperature and relative humidity allow you to calculate the dew point, and the two temperatures and 2  R values allow you to calculate the surface temperature of the inside of the glass.

Condensation is less likely with lower room humidity, warmer outside temperature, higher R value windows (e.g. double glazed), and lower R values for the insulating shutter.  You also get less condensation if the insulating shade fits tightly enough to reduce air flow between the shade and the window.   So, by playing around with these values, you should be able to find something that works in your situation.

Climate has a big influence -- our area is so dry that even though we routinely get below zero F temperatures and have high R value thermal shades, we rarely get condensation -- occasionally on VERY cold mornings we do get some beautiful frost patterns on the inside of the window glass.

Anyway, thanks to Dave for going the extra mile.

Gary