Some Observations on Generators and Capacity

Back in our last blackout, four months ago, I posted this about the distributed generation that thousands of West Virginians put in place to provide electricity when our Ohio power companies fail.  By the way, we in lightly hit southern Calhoun County remain without power this morning along with more than 200,000 others in worse hit parts of the state.

Because there has been no sun in the past few days, we have been watching our power usage and the behavior of our battery system closely.  Everything is still fine, and the voltage from our batteries is holding up well.  Sun is predicted for tomorrow and the weekend, so we should be fine.

But the calculations that I do in monitoring my system revealed something very interesting to me about the impact of batteries on generation capacity.  If you are a regular reader of The Power Line, you know that generation capacity is a big issue for power systems, whether they are big (like PJM) or still pretty big (like WV), but capacity is also an issue for small distributed systems, along with fuel costs.

I live in a poor part of WV, so my neighbors do not have whole house generators or lots of electrical appliances.  We also live in an area where local land owners have retained control of at least some of our natural gas resources through free gas clauses in leases, so many people have gas heat and water heaters.

So let’s look more closely at the generator/battery situation.  We have a 5000 watt gasoline generator.  When my battery charge gets low, I can plug my generator into my system and restore my batteries to a full charge, ready to go for another 10 days with sun or 7 days without any sun.  That deep charge process takes about 2 hours, with the generator running at full 5000 watt output capacity.  The charging process uses less than 2 gallons of gas and uses the full capacity of my generator.

My neighbors run their 5000 watt generator all day.  My critical loads pull an average of about 200 watts per hour (.2 kw per hour) from my batteries, or about 4.8 kwh per day.  Even assuming that my neighbors are using 1 kw per hour, they are still running a generator at only 1/5 of its capacity for at least 15 hours per day.  Part of the issue, of course, is that they need extra capacity to handle peak loads when an electric motor kicks on in their refrigerator or water pump.  At most, those peak loads last less than a minute.

So we see a microcosm of larger power system issues even in our small household systems: too much capacity, wasted fuel.  The other problem is with electricity use.  Most people just back feed their generators through their main breaker panels and continue using electricity the way they always do.  Maintaining only a few circuits on a critical loads panel during power company failure automatically limits electricity use.  It cuts our already low use about in half.

So the investment in the battery system, even without the generation of new power from our PV panels, creates a much more efficient use of our gas generator capacity.  When we need it, we run our generator at full capacity and then shut it off, cutting fuel costs and wear and tear.

The problem with all gas generators, ours included, is that when they aren’t running, they represent a cost that can’t earn you extra money.  That is where my PV panels provide the extra kick.  They charge my batteries when Mon Power fails, and when Mon Power is running, they continue to electricity that is immediately available for my use.

As I have said repeatedly, it is important that we learn from our experiences with distributed generation so that we can all become better engineers of our own power generation.

The power companies want us to remain stupid consumers, as the mercy of their failed systems, but those days are over.  We need WV owned and operated power systems, and we are building them one system at a time.

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