Designing Farm Scale Off-Grid Systems

Designing a properly functioning off-grid energy system can be a challenge, especially in northern climates where the sun's energy is so seasonal. Currently one of the best ways to create continuous renewable energy year-round is using micro-hydro, which involves placing a small water-powered generator into a water line fed by redirected water from a stream. Unfortunately, few people have access to a suitable stream, and micro-hydro systems are fairly expensive.

By far the cheapest renewable energy source to date is solar panels which convert the sun's energy to electrical energy. In northern climates, unfortunately, the amount of sun hours are very minimal during the winter season. For a solar system to be large enough to provide enough power during winter, it would generally need to be sized so big that there would be a lot of energy waste in the summer time, which is generally not economically viable.

There are a number of ways to deal with this problem. One option is to add another renewable power source, such as a wind turbines. This may be a very good option in some situations, especially if you live in a very high wind area. Unfortunately, for wind turbines to be effective, they need to be sited properly and at the correct height, which often adds a lot of cost to the system. In an off-grid system, this high cost may be a worthwhile investment, but it generally will not eliminate the need for fossil fuel electrical generation since there are generally extended periods in winter of both low solar and wind energy.

Ultimately the ideal scenario would be a means of storing excess energy produced in the summer for use in the winter. Current grid-tie regulation allows for this, but for off-grid applications, there is currently no economical means of storing that amount of energy long-term. However, significant advances in energy storage is underway, and it is very difficult at present to know how quickly large-scale energy storage may become viable.

Our current recommendation for farm-scale off-grid systems where fossil-fuel generation is required to offset short winter days is the installation of a micro-CHP system. CHP stands for Combined Heat and Power. A normal generator running at optimal load will have a maximum efficiency of 30-35%. The rest of the energy produced is wasted in the form of heat. A CHP unit captures this heat energy for use in buildings or other heating needs. This is ideal for the northern off-grid environment, since both heating and electrical supplementation is required in winter. Call for more information on micro-CHP options available.

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