Restoring an Elec-Trak Tractor and Integrating it With Our PV System

Last summer, we bought a used Elec-Trak tractor -- I suppose "used" is a bit redundant since the last Elec-Trak left the factory in the 80's.

Our "new" Elec-Trak after some TLC.

The Elec-Traks are all electric tractors powered by a set of on-board lead acid (golf cart) batteries.  They were made by GE for several years during the 70's, and were popular with more than 30,000 made.  They are very durable and functional machines with a wide range of all electric accessories.  The Elec-Traks have a strong following with an online owner forum and good parts support.   Many of these tractors have been rebuilt and are serving people well.  Being electric, these machines are cleaner, cheaper to run, and low maintenance than equivalent gasoline models.

The Elec-Trac with new charger/inverter supplying 120 VAC power out in the field.

In addition to the usual mowing and snow blowing tasks, we wanted to be able to use the Elec-Trak to power our home during power outages -- it has a large enough battery pack to power a few critical loads like the fridge and furnace for something in excess of a day.   This proved to be a relatively easy thing to do using a commercial charger/inverter from Tripplite.

In addition,  we wanted to work out a way to use our grid-tied PV array to charge the Elec-Trak battery pack during power outages.  This proved to be more of a challenge in that grid-tied PV arrays are designed to stop operating as soon as a power outage is detected, and to stay offline until the grid comes back.  After a bit of head scratching, we did work out a way that is fairly easy and effective if not terribly elegant.  The nice thing about our arrangement is that we get most of the benefits of a grid-tied with battery backup PV system, but without the considerable initial expense of these systems and without the need to maintain and replace a set of batteries that is almost never used.  See the link below for details.

Charging the Elec-Trak batteries during a simulated power outage using our PV array.

All the detail on our Elec-Trak project -- from scraping and painting to integrating it with our grid-tie PV system -- about 20 pages in all...

More Elec-Trak stuff:
For a rundown on the history of the Elec-Trak and a description of the various models, see Mark's article...

The Build-It-Solar section on Elec-Traks and similar electric machines...

One of my favorite Elec-Trac sites is George's My Elec-Traks site...  He has restored just about every model and also has lots of the Elec-Trak manuals and brochures.

The online Elec-Trak owners forum...

Just a bit of rust to clean up.

The new charger/inverter rides with the Elec-Trak when power is needed for 120VAC loads, or can stay back in the barn for charging.

The new charge controller that allows the grid-tie PV

array to temporarily be used as an off-grid PV array to charge

the Elec-Trak during power outages.

Gary

December 21, 2011

Solar Site Survey Based Aerial Photos

Bright Harvest offers a somewhat unique solar site survey.  They use aerial photos of your house to build a digital model, and then show you alternative arrangements of collectors.  They also model any shading objects near your home, and show the monthly and yearly effect of this shading on the output of the array.  Estimates for yearly output are also shown.

Overview of the model and panel layout with shading.

They offered to do a survey of my house, and I took them up on this and the link at the bottom of this post is to a page with the details on the survey and some thoughts on it.

In a nutshell, I was favorably impressed by the survey.  They did a good job of identifying potential PV array placements and a good job of finding shading sources.  Even though I've done a couple "manual" solar site surveys on my home myself, they found some things that I had missed or not thought about.  

The cost of the survey is not trivial at $150, but it may well be worth it to get a good handle on shading -- especially for complex situations.

I would always recommend doing the "manual" solar site survey yourself, as it will make you aware of how the sun interacts with the house and shading objects over the course of the year -- its just something everyone should do before tackling any solar project.  But, if you are uncertain about the shading situation or array mounting possibilities after the manual survey, the Bright Harvest survey or a SketchUp model would be a very good follow up.  I get a lot of emails from people who put their collectors up, and then come to find that the shading situation is worse than they thought -- it is just very important to have a good handle on shading before starting.

Full details and comments on the Bright Harvest report on my house...

The "manual" solar site survey you can do....

Gary

December 16, 2011

DIY Solar Garden Helper Machine

This is Randy's pretty amazing solar powered garden helper machine.

Randy made the machine to make it easier to do the planting, weeding and picking chores in the garden.  The seats on each side are adjustable side to side to accommodate wide or narrow rows of plants.  The speed control is a joystick that can be mounted left, right or center.

The frame is made from 1 inch welded steel tubing.  It is solar powered using 4 golf cart batteries and two on board 80 watt PV panels that also provide shade for the driver.

The drive train is from an electric wheelchair, but is geared down for more torque.  Maximum speed is about walking speed.

Thanks very much to Randy for making this available!

All the details on Randy's solar garden helper machine...

More solar powered garden tractors and lawn mowers...

Note the batteries over the rear wheels for more traction and
less weight on front wheels for easier steering.

Gary

Greenstar Blox -- A New Energy Efficient Wall Block

Greenstar Blox are a new wall building product that has been under development for several years.  The Greenstar Blox offer the promise of high strength, durability, high R values, reasonable cost, and a relatively straight forward build process.  It looks to me like they might make a good material for owner built homes.

A Greenstar Blox project

The standard Greenstar Block is 10 by 14 by 4 inches and is made from roughly 65% selected recycled paper, 25% Portland cement, and various additives.  This is similar to papercrete, but the difference is that Greenstar Blox are commercially made to a standardized recipe  using  a standardized process to produce a consistently high quality block.  The Greenstar Bloxs are currently going through an extensive testing program at Texas Tech University.  The results of the testing program are being used to seek building code approval, which is anticipated in early 2012.

The blocks are laid in courses as usual (kind of like Legos).  The mortar is made from the same
material that the blocks are made from.

The blocks appear to be relatively straight forward to build with.  They are much lighter and easier to handle than concrete blocks.  They offer the big advantage of a high R value right in the block without the need for additional layers of insulating material.   Greenstar says that walls made with their blocks will be about R25.  


An important item for anyone thinking about building with these blocks is that building code approval is in the works -- this will make it much easier for people wanting to build to get building permits.


I'd love to hear from anyone using the Greenstar Blox.


Notes from a consversation with Greenstar Blox...


The Greenstar Blox website...


Gary

Boat in a Hole -- George's Unique Rootcellar

Could not help passing this on.
This is George's solution for a cost effective, relatively easy to build, and very functional root cellar.

After thinking about a number of ways to build a root cellar for their new place, they tumbled to the idea of using a fiberglass boat hull.  It turns out these are available for reasonable prices.   They provide a good, waterproof and strong root cellar.

Buried for root cellar use.

They use it for both a root cellar and also as a bunkhouse.

The entry.

While I suppose this might seem a bit sad to some boat owners, George points out that there are a number of derelict boats around that will never see use again, and this is a 2nd life that I'm sure any boat would like a lot better than just rotting away unused.

George's full description of the boat for root cellar...

More on various root cellar designs...


Gary

Flow of River Hydro -- Using Only Stream Velocity to Drive a Turbine

I get email questions from people who live on a stream and would like to use the stream to make electricity.
If the stream has some elevation drop over the property and the flow is decent most of the year, then the answer is that if you can meet the legal requirements, its possible to make electricity, and that it can be quite cost effective.

Quite a nice underflow water wheel.

But, if the stream has no elevation drop, and you just want to make use of the velocity of the stream water to make electricity, then its more challenging.  I've added a new section that goes into what's involved in generating electricity only from the water velocity.  It covers how to estimate the amount of power your stream might generate, provides a bit of design information, and it lists all of the home scale example projects I could find that seemed like they might actually work.  Its a place to get started on your quest for free no pollution energy from your stream.

One of the reasons getting power from your stream is difficult is that while its clear that there is energy in that flowing water, it not nearly as dense as the energy you can extract from water dropping through an elevation difference.  This plot shows you roughly how much power you can get from 1 sqft of flow area at various stream velocities.

Just a glance will tell you that if you have a 2 mph 6 inch deep stream, your power generation possibilities are pretty limited.  But, if you have a deep 5 mph stream, there is some worthwhile power there.

I found a few commercial and few homemade examples of flow of river turbines and water wheels -- the link below provides pointers to all the ones I could find.  If you know of others please let me know.

The new section on Flow-Of-River hydro installtions...

The micro-hyro page for info on more conventional hydro...

Gary

Bottom-Up Insulating Shades for Light and Insulation -- Our R8.3 Window

On some of our windows that we have no need to look out of, but still want some light, we use a 3/4 insulating shutter on the bottom of the window.   I like the 3/4 shutter idea because it does a very good job of insulating most of the window, while still letting a lot of light into the room.

The 3/4 shutter got us to wondering if a top-down/bottom-up insulating shade could be used in the same way -- we decided to try this on one of our windows.

Our first try at an insulating top-down/bottom-up shade.

This window is a bit odd with the triangular top, and I had to add a support board to hold the top bar of the shade in place.

This arrangement allows us to have the shade fully up at night for privacy and maximum insulation, or during the day to have the shade part way up to allow more light and views with some insulation.  Normally we would have it up more than the picture shows during the day to get somewhat more insulated area.

The new shade is from Symphony Shades and in addition to being a good double cellular insulating shade, it has side tracks that reduce air flow around the sides of the shade.

The side tracks prevent airflow around the edges of the shade.

Closeup of track showing notch in shade that track engages.

It turns out that this window already has a double Mylar inside storm window on it (bet you could not even see it :), so the total insulating value is:  low-e window (R3) + double Mylar storm (R2) + insulating shade with side tracks (R3.3) is a sort of amazing R8.3!

Gary

Large 1986 Solar Space Heating System Marches On

In 1986 Mike Smith built his own home.  The home included very high insulation levels and a large (360 sqft) solar air heating collector.  

Mike's home with the large solar air heating collector.

After 25 years of service, the collector is still going strong.  Amazingly, in 25 years the system has required zero maintenance.

The hot air from the collector is ducted down to a rock bin in the basement to store heat.  When the house needs heat, hot air from the rock bin is ducted to the house.  A regular furnace provides backup.

The very good insulation levels (especially for 1986) allows the solar heating system to provide a large fraction of the home heating.

Mike provides all of the details on construction and living with the system for 25 years are here...

Lots more on solar space heating of all types here...

More examples from people who built great solar homes...

Gary

How Much Money Do You Save Installing Your Own PV System?

When we did our PV system two years ago, I did not really have a good way to evaluate how much money I saved by doing the install myself, let alone how this might vary over the country.  I knew how much it cost me, but, I did not really have a good number on how much an equivalent professionally installed system would cost.

Our 2.1 KW micro-inverter DIY PV array.

The Nov/Dec issue of Solar Today answered that question by providing a state by state installed cost per watt survey.  The current US wide average turns out to be $6.80 per peak watt.  

So, armed with this new data on what professional installs typically cost, I decided to update what our PV array would cost at today's prices and compare that to the $6.80 average professional install.  The results surprised me a bit.

Using the latest prices, a setup similar to what we put in two years ago would be about $3.30 per watt.  So, the savings for for DIY install is a bit over 50%.  For the 2300 watt system I looked at, this is a bit over $8000.  Not exactly chicken feed.

All the details, cost estimates, etc.   are here...

All the details on the PV array design and build are here...

Being a fan of solar thermal I'll just mention that that the cost per peak watt for our $1K Solar Water Heating system is less than 50 cents a peak watt  -- Holy Cow! :)

Gary

Solar Water and Space Heating Project With Unique Collector Design

Rob's new solar heating system provides both solar space and water heating.  The system is based on the $1K drain back design, but incorporates a number of very interesting design variations that may be helpful if you are doing a system.

Rob's finished system with the two hizer design collectors.

Side view of the collectors.

One unique feature of Rob's system is that the collector uses the new hizer design.  In most collectors the finned tubes that absorb solar radiation and transfer it to water flowing through the tubes run vertically with manifolds along the top and the bottom to supply water to the riser tubes at the bottom and collect heated water from the riser tubes along the top.  The hizer design was invented by Alan Rushforth to provide a more efficient design for wide collectors.  In the hizer design, the "riser" tubes run horizontally and the supply and return manifolds run vertically along the left and right sides.  The resulting horizontal risers have been dubbed hizers.  The hizer design results in shorter manifolds, and fewer riser to manifold connections -- a saving in both material and labor costs.   I

Rob's collectors are the first ones I know of to use the hizer design in a drain back system.  In order to insure that the collector water drains back to the storage tank (for freeze protection), all of the hizer runs are sloped slightly downward toward the supply manifold.

One of the collectors showing the hizer arrangement.

While Rob used two 10 ft wide hizer collectors, it would also be feasible to build a single 20 ft wide hizer collector.  For large solar space heating applications that might now use 5 or 6 or more side by side 4 ft wide by 8 or 10 ft wide collectors that must all be installed separately and plumbed together, the hizer design offers the possibility to build one large collector in place with with 25 or more ft long horizontal hizers instead of many many vertical risers.  It could be a real plus for wide, large site built collectors.  In addition to the saving in time and material, it is believed that the hizer design will be easier to get even collector filling and flow.

This shows the vertical manifolds being laid out.

Rob did a very careful job of working out the structural and plumbing details for the system, and much can be learned by just going through the detailed construction pictures and seeing how Rob handled the various construction details.

For space heating distribution to the house, Rob will be using a water to air heat ex changer mounted in the furnace ducting.  He plans to make some use of this same heat exchanger for summer cooling using well water.

Full details on designing and building the system...  (including a 42 page pdf)

Many other solar water heating systems...
Many other solar space heating systems...

An example of closed loop hizer design from Bob...

Thanks very much to Rob for taking the time to carefully document the system!

Gary