Monday, October 01, 2007

Off-Grid vs. Grid-Tied, My Survey

By more than a two to one margin, visitors to my blog prefer grid-tied over off-grid. This came as somewhat of a surprise to me. I expected more people to opt for off-grid. I thought that being self-sufficient and having a reliable source of electricity would have steered more folks toward an off-grid system. I chose off-grid because of budget constraints, and because of an unreliable grid. I was able to build a “starter” system on a small budget, and as a result I have a limited amount of power when the grid is down. My goals were; to avoid being in the dark, to have the capability to keep warm in the winter and cool in the summer, to keep food from spoiling, and to have the limited use of other appliances. I’ve already met those goals to a certain extent. My small system can’t keep up during temperature extremes or during extended periods of cloud cover, but its benefits are impressive nevertheless when considering the size of my investment. And it’s always exciting when I upgrade the system and extend its capabilities. (I don’t know how I’d amuse myself if I were rich).

If money were no object, I’d opt for a grid-tied system with batteries. While such a system provides the best of both worlds, it is also the most costly. A grid-tied system with batteries must be able to automatically disconnect from the electrical grid when the power fails. If not, it could be dangerous for utility workers in the area. As a major advantage of such a system, it uses all of the free-power available, only switching to costly grid-supplied power as a last resort. Switching is automatic, based on setup parameters. The system can be set to be very gentle on the batteries, extending their life, or be set to use them to a greater extent, resulting in a lower electric bill. It must be great to have choices like that!

I think it’s reasonable to assume that while grid reliability problems may increase in the future, the grid is never going to disappear completely. As long as it is there part of the time, those attached can take from it and contribute to it. And those who supply power to the grid are paid, or at least credited, for their contributions. So unless electric rates or grid-connection charges are prohibitively high, being grid-tied makes more sense from a financial standpoint than an off-grid system does. And since an off-grid system with batteries efficiently uses the energy generated by the sun, it’s a good “green” choice.

While a batteryless grid-tied system is efficient and cost-effective, it must be embarrassing to have a large PV array, but no power when the grid goes down. What would the neighbors think? Still, this type of system is the best “green” choice, and it requires the least maintenance. On the other hand, I like my independence. If I could disconnect from the grid completely, I’d do it, even though that is not the most economical way to go. Unused power is wasted, so it’s a challenge to use as much of it as possible, while not stressing my batteries. I like the idea of using free energy from the sun, and not from a coal-burning power plant. I’m being kind to the planet, and preserving natural resources for future generations. Perhaps even more importantly, I’m setting a good example. Some things are more important than saving money.

John

7 comments:

d said...

Hi SJ,

If you'd given the option of 'both' I'd have chosen that instead of grid-tie.

I'd like to keep a small completely autonomous off-grid system for lighting and charging mobile phones and other odd and ends like I have now. This is effectively optimised to provide 'enough' energy mid-winter, not maximum all year round.

But I'd also like a big grid-tie PV array that I can optimise to pump as much energy into the grid as possible so that during the course of a year I could neutralise all of my electricity use (be a net generator) and some of my power use from other sources (eg gas for heating) in terms of CO2. Having trimmed our domestic electricity consumption to ~7kWh/day I could just about do this with the maximum that I'd be allowed to connect to our local grid, ie about 4kWp. That helps avoid the lights going out in the rather longer term I hope.

Rgds

Damon

Anonymous said...

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Anonymous said...

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I would appreciate if a staff member here at solarjohn.blogspot.com could post it.

Thanks,
Charlie

Anonymous said...

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Anonymous said...

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I have a inquiry for the webmaster/admin here at solarjohn.blogspot.com.

May I use some of the information from this post right above if I give a link back to your site?

Thanks,
Peter

John said...

Peter, I am always glad to have links back to my site. You may use information as you requested, with a reference to where the information came from. Thanks!
John

Anonymous said...

Hello there,

This is a question for the webmaster/admin here at solarjohn.blogspot.com.

Can I use part of the information from this blog post above if I provide a link back to your website?

Thanks,
John