There’s no better place for watching sunlight turn into electricity than a garden—plants, after all, are just living solar panels, capturing light and turning it into the energy that fuels life itself. So there’s a kind of synchronicity in turning to the sun when you need power in the garden.
At its simplest, using solar energy is as easy as popping a cloche over a row of winter lettuces to trap and intensify sunshine on frosty days, heating up the ground enough to keep everything growing strongly. Photovoltaic technology is becoming so sophisticated and versatile that nowadays we can harness the sun’s help for dozens of garden applications, from raising seedlings to lighting a path to powering the drill you use to build raised beds.
At the moment, the default setting for powering everything from heated propagators to the radio you listen to while you’re working in the greenhouse is conventional electricity or batteries—plug it in, flick a switch and you’re cooking. But that’s like getting out the Chevy to drive the two-minute walk to the store.
There’s a mismatch between what you need to do, and what you’re doing it with. In a garden, where you use a relatively small amount of electricity at intermittent intervals, you have all the energy you require already installed, and it’s shining out of the sky onto your head.
Solar power is the obvious solution to so many of our gardening needs. You don’t need massive solar panels or complicated installations to power something as small and energy-efficient as a light, a garden fountain or a water pump—panels for this sort of application can be small enough to nail to a fence post. The smallest panels are often incorporated into the fitting itself.
Sometimes it’s such a natural fit, it’s hard to see why we’d do it any other way. For example, automatic irrigation kits that only turn on when it’s hot and watering is required, or fountains we only want to bubble on warm, sunny days when we’re around to enjoy it. But solar power can boost electricity supply when it’s cooler, too.
That’s because photovoltaic solar panels operate on light, not sunshine, and light still reaches the ground even when it’s cloudy, though usually at lower concentrations. That may cause difficulties if you’re trying to power a house, but if all you want to do is run a power drill, it’ll charge up a battery well enough.
Photovoltaics are less efficient in winter, when light levels can drop to a third of summer levels as days shorten and the sun weakens, but you can still use solar power to heat your greenhouse in the depths of winter, even when the snow is thick on the ground outside, by using passive solar power.
Also known as solar thermal energy, this is the low-tech end of solar power generation and easy enough to set up yourself without any special equipment required. The idea is that you capture and intensify the heat from the sun, a little like you do when using cloches, and direct it into something dense that stores the heat and releases it slowly—usually soil, water, bricks or concrete.
If you have a greenhouse, you already own a giant solar panel. Just putting it up increases temperatures inside about 3-5 degrees above ambient air temperature outside. If it’s a lean-to greenhouse, capitalizing on the heat-retaining capacity of a house wall, it’ll hold onto that raised temperature for much of the night, too.
You can boost this even more by installing the equivalent of a solar-powered heater in your greenhouse. Paint a metal radiator black, put it inside and hook it up to a circuit of metal plumbing pipes running under a seedling bed. As the winter sun heats the radiator, it warms the water inside.
This sends it around the circuit, delivering a steady warmth to your young plants—your very own homemade, solar-powered, heated propagator. The same effect can be used to generate general heating, too. Fill black-painted barrels with water and stand them in the greenhouse. They’ll heat up rapidly in the most fleeting of sunny spells and then slowly release the heat into the air, keeping it frost-free even on the coldest days.
source: Maximum Yield