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Making Solar Accessible

Whole house solar systems are great for those who can afford them, but what about those who can’t?

Several converging developments have recently made a new type of renewable energy installation affordable and practical. Due to the decreasing cost of electronics, a new breed of digital, low power, high-efficiency battery charge controllers have come onto the market. LED efficiency has increased and the price of solar panels has steadily decreased. In combination, these advancements allow for modular renewable energy. This is not a system that lights up a city, or an office, or a house, but a system that lights up a single room, to be installed directly where it is needed.

The latest generation of small charge controllers incorporates traditional features such as a charging light and overvoltage protection (which prevents the battery from being overcharged). More advanced models also include battery state-of charge indicators and low voltage disconnects (which also protects the battery).

The most important advancement though is the incorporation of Pulse Width Modulation (PWM), which was previously unaffordable for low-power controllers. Pulse width modulation makes charging much more efficient by switching power delivered to the battery on and off very rapidly to create an average voltage lower than the full voltage of the panel.

Until recently LED outputs were low enough so it was difficult to obtain bright light (i.e. equivalent to one or more 60W incandescent) without a ludicrously large and electrically complex array of LEDs. Individual LEDs now approach 300 lumens (or about 1/3 as bright as a 60W incandescent) or more.

Photovoltaic panels are getting less expensive in large part due to economies of scale obtained because of ever-increasing demand. While this makes an individual solar panel affordable to the average person, what use is one solar panel? Clever people have certainly found practical uses for a single panel, but wiring one up with an inverter in order to add power to your home is not one of them. At the same time, lighting companies are developing LED replacement lightbulbs, which must incorporate rectifiers to convert 120 volt alternating current (standard for houses in America) to direct current, which is what LEDs need. So, if you had a solar power system in your house, in order to use a light, you would be generating direct current, using an inverter to change it to alternating current, and then sending it to a lightbulb which is changing it back to DC current by using a rectifier. (Expensive and inefficient!

A modular solar lighting product can cut out the ‘middle-man.’ It generates direct current, stores it with a small digital charge controller, and small sealed lead-acid battery (which have also developed in recent years to the point of being maintenance free over their lifetime). Take the direct current out of that battery, and send it directly to a small array of high-power, high efficiency LEDs. No converting to alternating current and back is necessary, which saves equipment costs and energy. Furthermore, these systems are very easy to install, typically taking only about two hours to complete.

These modular systems can’t make a home energy-independent like a whole house system can, but they are a step in the right direction. They can also be particularly cost effective to light a basement, shed, barn, playhouse, camp, boat, RV, or added anywhere a new source of light is needed. Moreover, modular lighting systems enable those who cannot afford to buy a whole house system to purchase solar lighting for one room, and support renewable energy, while reducing our dependency on a fossil-fuel powered grid. Given the price range of modular solar products (mostly between 250 and 400 dollars), about 60-80% of U.S. households could purchase one without spending more than 1% of their annual income. Using similar criteria for a whole-house system, only the top few percent of the highest earning households could purchase one.

Obviously, there are plenty of people ready to shell out more than 1% of their annual income for solar, but this explains how modular solar could be easily and affordably adopted on a large scale.

The founders of Yeti Solar believe so strongly in the value of this technology that the production and distribution of low cost modular solar has become the company’s primary mission.

by Rustom Meyer, MEng and Jon Meyer, MID – Yeti Solar founders

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