Tuesday, September 27, 2011

PV Systems for Homeowner Installation

I added a new section on the PV systems that are just beginning  to come out that are aimed specifically at being installed by the homeowner.  They are small grid tied systems that use microinverters to simplify the systems and to allow one to start with a small system and then easily expand it over time.

The recent news in this area is the announcement from Westinghouse on their new set of systems for homeowners:

Westinghouse announced the release of solar PV kits for DIY installation.  The kit includes the PV modules, microinverters, parts for roof mounting, and the other bits needed to complete the system.  

It appears that each PV module mounts to the roof independently, and that the mounting hardware is included.  It appears that the microinverters are integrated with the PV panel.  The kits will be offered in 3 sizes: 1 panel, 4 panels, and 20 panels, where each panel is 235 watts.  As with all microinverter based systems, it is easy to expand the sytem.

The Westinghouse Solar website provides more information on the system.  There are some resources for DIYers, and what looks to be a detailed and well written installation guide.   Westinghouse appears to be pretty serious about this effort.

The Westinghouse sales person told me that the systems can be ordered via Lowes Hardware, and the the cost for a 4 panel (940 watt) system is about $2600.  This does not include the Enphase EMU monitoring unit, which many people will want to monitor the system.
The system is based on the Enphase microinverter -- you can get a detailed understanding of how this system works and goes together by reading the first two entries in the Grid Tied PV section ...

I would love to hear from anyone who gives this system a try.

Some additional systems and approaches are listed in the new section...


Saturday, September 24, 2011

The Sungrabber Unglazed Solar Water Heating System

The Sungrabber is an interesting newish commercial solar water heating system that makes use of unglazed plastic collectors (pool heating style collectors) rather than the traditional glazed flat plate collectors -- this allows a substantial reduction in the system price.  
Just to give an idea of the potential, unglazed plastic collectors sell for about $5 per sqft while traditional glazed flat plate collectors are about $30 a sqft.

Their website is: http://www.sungrabber.net

This diagram from their website shows how the system works:

The collectors are unglazed plastic pool heating style collectors.   The system is a drain back system, meaning that when the sun goes off the collector, and the pump turns off, all of the fluid in the collector drains back to the drain back tank -- this is a well established method of providing freeze protection and works well even in the coldest climates.  It also means that plain water can be circulated through the collectors, and the hassles of dealing with antifreeze are avoided.

To transfer the collected heat from the collector loop to the hot water tank, the collector heated water and the water tank water are circulated through a heat exchanger in the the "Circulation Module".

Of course, with unglazed collectors, performance will suffer dramatically in colder climates -- the link below gives a rough estimate on how much. 

But, the system price is much lower, and in spite of the hit in cold weather performance, in many climates the payback period will be substantially less than for a conventional $8000 commercially installed solar water heating system.  

It seems to me that the solar water heating industry has been in a bit of a rut (an expensive rut) for some time, and this kind of system shows some good innovation -- it would be nice to see more of this.

This would make an ideal DIY solar water heating system, as it looks to be relatively straight forward to install.  I don't know if Sungrabber offers it this way or not.

There are some other interesting DIY versions of the system.  For example, the regular $1K DIY drain back system could be set up with the same kind of unglazed plastic mat collectors.  This would significantly reduce the work involved, and it would result in a system that was somewhat more efficient than the regular Sungrabber system as the storage and collector area could both be pushed up some with very little cost increase.   
In an interesting twist, I believe that if one used an SRCC OG100 certified unglazed collector (of which there are many), the full cost of the $1K system would qualify for the 30% federal rebate!   This would get the payback down to less than 2 years for many people.   State rebates might further decrease the cost getting it down near the zero area in some places.


Friday, September 23, 2011

The Solar Decathlon is Starting

The Solar Decathlon is starting tomorrow, September 23, 2011.

There will be teams from 20 universities around the US and the world with full sized demonstration homes that aimed at winning the decathlon competition that emphasizes energy efficiency and sustainability.

This from the Solar Decathlon website explains the decathlon:

The U.S. Department of Energy Solar Decathlon is an award-winning program that challenges collegiate teams to design, build, and operate solar-powered houses that are cost-effective, energy-efficient, and attractive. The winner of the competition is the team that best blends affordability, consumer appeal, and design excellence with optimal energy production and maximum efficiency.
The first Solar Decathlon was held in 2002; the competition has since occurred biennially in 2005, 2007, and 2009. The next event will take place at the National Mall’s West Potomac Park in Washington, D.C., Sept. 23–Oct. 2, 2011. Open to the public free of charge, visitors can tour the houses, gather ideas to use in their own homes, and learn how energy-saving features can help them save money today.


The Solar Decathlon:
  • Educates student participants and the public about the many cost-saving opportunities presented by clean-energy products
  • Demonstrates to the public the opportunities presented by cost-effective houses that combine energy-efficient construction and appliances with renewable energy systems that are available today
  • Provides participating students with unique training that prepares them to enter our nation's clean-energy workforce.

There are some interesting looking projects this year, and it appears that this year there is quite a bit more detail on the features used in each project -- this is a very welcome improvement.
Have a look on the Teams link for each team for the Construction Documents.

The decathlon is at the National Mall's West Potomac Park in Washington, D.C., Sept. 23–Oct. 2, 2011.

University of Calgary entry
I'm going to try to take some time to go through each entry and pick out the features and projects that might of of particular interest to the Build-It-Solar folks.


Saturday, September 17, 2011

The Black Side Pool Heater

This is a really simple idea for heating an above ground swimming pool from Deane:

From Deane:
I had been heating my above ground 24 foot x 4 foot swimming pool in NH  with some eight 4x10 roof mounted pool collectors.   The roof faced west and had a 20 degree slope.   Needless to say early mornings and spring output weren't great.

One day I decided to paint the vertical south exterior  wall of the pool black.   Boy did that help.   First the wall was exposed to the April sun much more directly and throughout the day.  Second the heat transfer to the pool was great because the sun struck the  black metal pool wall directly and the only thing between the heated wall and the water was the very thin 20 mill pool liner.    In spring the object is to get the water up from freezing so the pool wall barely runs above ambient air during the day resulting in near zero loss back to the air. 

In my case I doubt the addition of a glazing would help much although it might be worth it as the pool temp rises to swimming level.

Of courses the pool heat losses were the same.  

In summary the cheap black paint extended the season 3 weeks on either end. 

Imagine the effect if all above ground pools came with black exterior walls.   Even better if they were selective.

Further in summer the south wall of the pool got less sunlight so didn't overheat. 

September 12, 2011

I really like this -- its about as efficient a pool heater as you could devise, costs almost nothing, does not take up any space, and an HOA could not possibly object to it!

More details, thoughts, and heat saving estimate on this idea...

More solar pool heating projects...


Wednesday, September 14, 2011

Soda Pop Bottle Solar Light

This is a really simple and cheap idea to bring solar light into a dark room.

A regular 2 litter polycarbonate soda pop bottle is fitted into a sealed hole in the roof.  The bottle is filled with water and a bit of bleach.  The sun shines in the top of the bottle, through the roof opening, and then the bottom of the bottle spreads the light around the room.  It is said to work much better than simple window in the roof.


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