Is solar power viable now?
by William Papolis, Monday Mar 26, 2007 10:34AM EST
Problems with solar power
One problem is, “what do we do at night?” We need a place to store power, right? Two possible methods of portable storage are “batteries” and “fuel cells”. Looking at these methods of storing solar power, the prospects are disappointing. Here are some of today's problems:
- Batteries and fuel cells have a low power density compared to oil (they are heavy compared to the amount of power they store. Ten times heavier than oil.) Source: Fuel Volumetric and Gravimetric Energy Density
- Batteries and fuel cells are very expensive
- Today’s most advanced batteries require lithium. There are only 2 known places that have significant reserves of lithium. (World Reserves: Bolivia-35.8%, Chile-39.7% according to this US geological survey on lithium
- Batteries don’t work as well in cold climates
- Battery round trip efficiency, solar-battery-electricity, is about 90% (or 10% loss). Fuel cell efficiency round trip from solar-hydrogen-electricity is 30-50% (or 50%-70% loss) according to this NASA report entitled "Round Trip Energy Efficiency of Fuel Cells"
For these reasons, let’s assume that solar power storage is currently not viable. So that leaves us with harnessing and consuming solar power by day.
Solar Power only during the day, is that still OK?
If we accept solar production only happens during the day, and that we transmit that energy as it is produced, do we still have a credible source of power?
To answer this question we need to consider WHEN power is consumed.
Consider this graph of daily electrical consumption …
Source: New York State Independent System Operators
Examining this graph we note the following:
- Midnight-5AM electricity consumption is 60-66% of peak
- 5AM-8AM (then on till 6PM) consumption climbs to 90% of peak and remains there (80%-90%) for the day
- 6PM-8PM consumption peaks at 100%
- 8PM-Midnight consumption begins a precipitous fall dropping to 70%
- Midnight-5AM again, consumption reaches its lowest level at around 60-66%
It makes sense to have alternate sources of power to fulfill our nightly needs. Without a storage solution solar power can’t be one of them. However, considering this data as typical (for daily consumption) it seems that our peak consumption coincides well with daylight. Solar power can help provide a portion of that extra 40% we consume during the day.
We may have a credible power source!
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