Can I Go Off-Grid With Hybrid Systems?

Hybrid wind energy systems can provide reliable off-grid power for homes, farms or even entire communities (a co-housing project, for example) that are far from the nearest utility lines. According to many renewable energy experts, a “hybrid” system that combines wind and photovoltaic (PV) technologies offers several advantages over either single system.

In much of the United States, wind speeds are low in the summer when the sun shines brightest and longest. The wind is strong in the winter when there is less sunlight available. Because the peak operating times for wind and PV occur at different times of the day and year, hybrid systems are more likely to produce power when you need it.

For the times when neither the wind nor the PV modules are producing, most hybrid systems provide power through batteries and/or an engine-generator powered by conventional fuels such as diesel. If the batteries run low, the engine-generator can provide power and recharge the batteries. Adding an engine-generator makes the system more complex, but modern electronic controllers can operate these systems automatically.

An engine-generator can also reduce the size of the other components needed for the system.

Hybrid Power Systems - Combine multiple sources to deliver non-intermittent electric power

Keep in mind that the storage capacity must be large enough to supply electrical needs during non-charging periods. Battery banks are typically sized to supply the electric load for one to three days.

An off-grid hybrid system may be practical for you if:

• You live in an area with average annual wind speed of at least 9 mph (4.0 m/s).
• A grid connection is not available or can only be made through an expensive extension. The cost of running a power line to a remote site to connect with the utility grid can be prohibitive, ranging from $15,000 to more than $50,000 per mile, depending on terrain.
• You would like to gain energy independence from the utility.
• You would like to generate clean power.

Hydro vs. Wind vs. Solar Power?

Here’s an excerpt:
No single RE source works best all the time in all situations. Hybrid systems often yield the best year-round performance. Wind and micro-hydro usually perform well during stormy periods, while photovoltaics work best in dry summer conditions with long sunny days. Photovoltaics have the benefit of no moving parts, no maintenance, high reliability, and a long life averaging about 25 years or more for solar panels.
In 2008 solar panel cost of about 250 Rs. per watt (remember that batteries and inverters will add significantly to this cost) has been steadily dropping as sales of solar cells have doubled every few years.
The recent invention of solar roofing panels and the introduction of major PV incentives in several countries are expected to continue to boost sales and significantly reduce prices over the next decade.

Advantages

Hydropower:

• Lowest cost per watt hour
• Usually a predictable year round power output
• Often does not require a large battery bank
• System is quiet and often can be made unobtrusive
• Typically low maintainance

Windpower:

• Low cost per watt hour in a good location
• Smaller systems can be low maintainance
• Predictable power output in some locations

Solar power:

• Can be used almost anywhere
• Extermely low maintainance
• Very long system lifespans
• Can be operated unmonitored for extended periods of time
• Predictable power output in most locations
• Simple installation
• Silent , unobtrusive operation

Disadvantages

Hydropower:

• Not suitable in many locations due to lack of resource
• Often requires substantial modification of water resource (except for in-stream type generators)
• Initial installation cost can be high if damming or dirtwork is required
• In colder climates, freezing of pipes, etc can be a problem
• Moving parts will eventually wear out

Windpower:

• Not suitable in many locations due to lack of resource
• Towering can be expensive for larger units, and may require heavy equipment to erect.
• Some people object to the tower aesthetically
• Birds of prey run into tower and guy wires (similar to but smaller than utility installations in this respect)
• Power output can be sporadic in some areas, nescesitates the use of a large battery bank and / or altrenate power source
• Many people report that considerable noise is generated in high winds
• Even routine, minor maintainance on a windmill can be difficult on the top of a tower. Systems to reduce / eliminate this problem typically add to the cost and complexity of the system.
• Moving parts will eventually wear out

Solar power:

• High initial cost for solar panels
• Power output can be variable in some areas, nescesitates the use of a large battery bank and / or altrenate power source
• Requires good solar exposure (not practical in shaded areas, etc.)

Each system must be optimized to the location and aplication for which it will be used. Installation and maintainance requirements can be a signifigant factor, and should be weighed heavily in the design process.
Hybrid systems using two or more of these power sources, or using a fuel powered generator as a supplement usually provide superior performance over a wide range of conditions.