Reading John Perlin’s latest blog about 6,000 years of solar energy, I am reminded how modern builders can rarely consider natural efficiency anymore when positioning a house. Sometimes regulated by local ordinances, most homes simply face the road, no matter which way it’s pointing.
Our house, for example, a 1966 rancher, faces due west, with the largest windows catching intense summer heat all afternoon and bitter wind in winter. (I made triple-layer drapes of old blankets and bed sheets to compensate for this layout boo-boo.) Trees, too, at most homes are situated for curb appeal, rather than strategically planted to block wind or sun.
At least 4,000 years ago, the Chinese built their roads wide, running east and west so every building benefits from a southerly exposure in winter. In the last 100 or so years, those building practices were all but abandoned in industrialized nations. Middle class Americans could build 5,000-square-foot homes facing any which way, so long as there was electricity and fossil fuels to heat, cool and light them.
Resurgence in popularity of solar systems to reduce electric bills or to transition to off-grid lifestyles has many folks wondering what to do about the weeping willow and magnolia shading the yard. My husband solved the solar-power/shade-tree dilemma for us last week.
I knew something was going on when I saw him grinning like a cat and digging through boxes we hadn’t unpacked since moving here more than 3 years ago. Strange noises came from the shop – hammering, drilling and sawing – that I haven’t heard for quite some time. He also came home from town with one of those heavy-duty lawn wagons that I had dreams of using to haul logs or rocks from the woods.
Then, in just a few days, there was a peculiar new appliance basking in the sunshine outside the shop. Darren calls it our new mobile, compact, solar-powered, emergency, energy-supply system that follows the sun to store power for lights, radios and other electronics.
Yay! We don’t have to cut down any trees to have solar power. We simply roll the cart to a sunny spot and adjust for every season and optimum efficiency. Plus, the cart and panels are easily moved into various positions to absorb the sun’s rays from morning to evening.
We can also pull it by hand anywhere to use power tools with an inverter. Darren built our 160-watt, 12-volt system of scrap materials and solar supplies we already had on hand. To use all new purchased materials, we estimate it would cost $750-$800 to build, about the same as a fixed solar rack system in the yard.
The advantages, however, of a unit like this are its portability and efficiency. It can quickly be maneuvered inside a garage or porch ahead of snow, ice or wind storms. Living in the Ozarks, we have plenty of experience with ice storms that coated our previous fixed-rack panels for days at a time.
At the end of the day, we roll the cart into the porch. Then, we plug in our 12-volt system to use in the evenings. When we want to use 120-volt devices, we plug an extension cord into the inverter in the cart.
Our unit charges two 6-volt golf cart batteries that are stored in a separate compartment to keep released gases from corroding the electronic gadgets. In the larger compartment is a shunt, amp and volt meter, 30-amp voltage regulator, PV disconnect switch, 12-volt fuse block, headlight with switch and a battery disconnect for an inverter.
Among our miscellaneous boxes of whatnot, Darren also found an antique 120-volt table lamp that uses a 12-volt bulb, the kind used in cars. After some minor electrical changes, it’s my new energy-efficient, bedtime-reading light. Darren also wired the house so we can connect the system to light fixtures in the kitchen, bathroom and for the laptop and Internet.
We got the cart at the local farm supply store for just over $100. Darren added brackets to keep the panels from bouncing around as we traverse our rocky ground. A stiff piece of cardboard wrapped in a shower curtain makes a great cover for when less power is needed.
Our system uses two solar panels, but could also be built to accommodate more. The 2x4 frame to hold the panel on the cart must be long enough to extend the panels almost flat-out. For our latitude, the panels adjust from 63 degrees in winter to 10 degrees in summer, with positions in between for spring and fall.
Those of us in the northern hemisphere point our panels due south. Those down under, point their panels north. Here's how to calculate the best angle for your solar panels:
- In the winter months, when there's less sun, take your latitude, multiply it by 0.9, and then add 29 degrees.
For example: if your latitude is 40 degrees, the angle to tilt your panels in winter is: (40 x 0.9) + 29 = 65 degrees.
- In summer, multiply your latitude by 0.9, and subtract 23.5 degrees.
- In spring and fall, subtract 2.5 degrees from your latitude.
This little cart, combined with our non-electric water pump, just put us a huge step toward disconnecting from the grid. Ah, there is something new under the sun after all.
For more photos, see our blog and here to watch a video demonstration.
Linda Holliday lives in the Missouri Ozarks where she and her husband formed Well WaterBoy Products, a company devoted to helping people live more self-sufficiently off grid with human power, and invented the WaterBuck Pump.