One great advantage of renewable energy is that it is available in times of need, or as a supplement or replacement to commercially available power. John has taken renewable energy one step further, and designed a system which provides portable power in times of disaster or unexpected circumstances, and is easily moved from one location to another.  South Florida, a haven for unexpected storms and hurricanes, is one area where a system like John's can be very beneficial.

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Portable Power

  By John U.

My first battery back-up system consisted of a Sea Volt 130Ah deep-cycle marine battery, a West Marine 5A multistep charger, a Portawattz 300W MSW inverter, a Blue Sea 300A master disconnect, a receptacle on a switch, a 12V cigarette lighter adapter, and a 12V Hella fan.  

I mounted the components on a piece of shelving using woodscrews and cable clamps.  The inverter case had to be taken off first in order to mount the base, but everything else attached easily.  Accessibilty of the bus bars allowed quick disconnects for rerouting or additions.

            This system powered small 120VAC and 12VDC loads including lighting and ventilation.  It had storage capacity but lacked self sufficiency, it depended entirely on local utility power.   My next goal was to produce my own power.   I looked at the available renewable energy options for my geographical location and decided to start with solar power.

My first solar panel was a Seimens SR50.  This 50 Watt panel was rated at 2.9A and available locally for about $375.  I purchased a second shortly after that online for about $275.  This gave me a 6A charging capacity.  These photovoltaic modules are warrantied for 25 years, justifying the initial investment cost.

Many factors influence the decision of where and how to position the panels.  The most efficient way is to mount the panels in the most favorable location for maximum contact angle with the sun.  At the time, I had access to a garage and driveway.  This yielded the design of a portable base array.  Modular in design, the array can be assembled and disassembled in minutes.  If permanent positioning is not feasible, this option permits ease of transportation and set-up for short term operation.

A salvaged printer base made a solid platform to mount a support structure wide enough to fit the panel frame.  The frame itself is 1.25” punched angle zinc, cut to size and fastened with wing nuts.  The pivoting axis is a 3/8” threaded rod which allows tightening at any desired angle between –45 and +45 degrees.  Lockdown wheels add to its stability on flat surfaces.

“Hurricane Station Zulu”, as I call it, is a water resistant, portable interface terminal.  Using a marine grade dry-box, I incorporated the 5A charger, 300W inverter, 12VDC outlet, and 300A disconnect.  I added a DC Ammeter, DC % Charge meter, bus bars, fuse block, and battery leads.  This all in one design offers the user the freedom of connecting to any 12VDC source to provide 120VAC MSW and 12VDC.  The charger keeps the bank full during times of inclimate weather or transportation.   It weighs about 10lbs.

I bought second Sea Volt 130Ah deep-cycle marine battery, giving the bank a 260Ah capacity.  At this point, I was ready to test the system.  I rolled the base array out of the garage, plugged the panels to the charge controller, then plugged the charge controller to the batteries.  I positioned the panels to face south and tilted the axis to match the August sun.  I checked all connections one more time, and turned the master switch on.  Putting a digital meter between the charge controller and the batteries, it read 5.8A during the pulse..True to its claim, the two Siemens panels produced close to 6A of clean, renewable power.

I moved into an apartment in October.  The most important aspect in chosing a semi-permanent location is direction.  Ideally, you want the maximum southerly exposure, through either the windows, yard or roof.  I searched for three months for an unobstructed southerly facing for the panels.  The best I could find was a second story, unobstructed southerly facing.  The good news is I can get up to six hours of constant coverage, the bad news is, they sit vertical.   The strongest sun angle occurred on the day of the winter solstace when the suns elevation was at its lowest of the year.  This location maximizes available sunlight, yet remains far from its true potential.  In the picture it is 5 p.m., the solar day occures from around 9 a.m. to 3 p.m.  This location gives me about 18Ah per day.

The distribution center was assembled from readily available components around the house and from Home Depot.  Wood screws and ½” plastic strapping secured each item in various ways.   I mounted the items to the ¾” plywood on the floor first, giving due consideration to the placement and position of each item and its intended function.  Masonary screws where used to affix the panel to the wall.  This design permits not only room for expansion, but a sturdy, portable power center made for easy transportation and installation.

The top row of three clamp lights are utilized for testing different types of lighting.  I have found the compact flourescent light (CFL) to be the most economical as far as energy usage is concerned.  A 15W CFL draws only 1.5A, yet produces 60W of light.  They are available in many different colors ranging from outdoor lights, that have more of the cool, blue wavelength of light, to indoor lights, that contain more of the warm, red wavelengths.  Incandescent lighting is used with a dimmer switch so I can dial down the heavy draw of each bulb in series.  At the time of this article, I’m using (1) 60W and (3) 15W incandescents for lighting and a Honeywell fan for circulation.  This is what I have termed “Sub” lighting, or, using just enough to see your feet with.  At this load, about 5A, I can light and ventilate the entire apartment (800 S.F.) adequately.  A 15A load would include the TV, VCR and stereo, creature comforts during a blackout are the fruits of your labor, but use them wisely.

In the center is a Flexcharge 7A charge controller that regulates the voltage (13.8-14.3VDC) from the panels to the battery bank.  The Flexcharge PV-7 uses pulse width modulation to maximize charging and minimize sulfation.  Charge controllers significantly reduce the risk of overcharging and damaging your battery bank. 

Power taps and a 120VAC dimmer switch provide low tech solutions for my current power needs.  Load consumption is noticeably reduced using compact flourescent bulbs, low amperage fans and dimmer switches.

Because the possibility will always exist of an electrical problem or chemical incident, special safety concerns must be addressed before the project begins and continually during its lifetime.  The safety equipment I use include;  two smoke detectors, two ABC fire extinguishers, neoprene gloves, full face protection, head protection with lighting, long-sleeve shirt, boots, and sodium bicarbonate (baking soda).  Adequate safety measures should be in place at all times, capable to control all forseeable situations. 

Below is a line drawing of John's portable power system.

Click on drawing to enlarge

This project started in June of 1999 and is ongoing.  Thanks to all who have endured my questions, cursing, and ignorance: Fred ,Terry, Rob, Randy and good old Dad.

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