Hair dryer

Re: Hair dryer

From a math point of view--Assume 1,500 watt hair drier running on an inverter--how large of battery bank/solar array...

Inverter ~85% efficient, 24 volt battery bank, C/8 maximum continuous current draw from flooded cell battery bank:

• 1,500 watts * 1/0.85 * 1/24 volts * 8 maximum discharge = 588 AH @ 24 volt battery bank minimum

Assuming 5% to 13% rate of charge for solar array:

• 588 AH * 29 volts charging * 1/0.77 derating * 0.05 rate of charge = 1,107 watt array minimum
• 588 AH * 29 volts charging * 1/0.77 derating * 0.13 rate of charge = 2,879 watt array ~cost effective maximum

Assuming used in winter with ~2 hours of sun per day with a minimum sized solar array, you could run a 1,500 watt load (without generator backup) at night/early morning around:

• 1,107 watts * 2 hours of sun * 0.52 system efficiency * 1/1,500 watts panel+charger derating = ~0.77 hours per day

May or may not be practical for your needs--but at least you have a rough set of figures for a pure solar RE solution.

For a more accurate estimate--you can use a Kill-a-Watt meter to measure the energy use (average watts, how many Watts*Hours per use) you use the hair drier (high and low settings). If you use the drier on low (say ~750 watts), you could use a 1/2 size battery bank. And depending on how long run the drier, you could possibly use a smaller array (also depends if you use the drier every day or every other day).

-Bill

Susan,

With off grid power--It is a matter of what your needs are... For example, there are hair driers with high/low power (1,500-1,800 Watts high, ~550 Watts on low). Can you use a drier when set to low power? If so, that will make the power "peak power" requirements 1/3rd as large. If you need the hair drier on high/full power, you are stuck with a pretty large off grid power system (or even a genset).

I looked around for what folks who live in RVs use--And there does not seem to be many options. There are 12 VDC "hair driers"--But between smoking when new and very low heat output (maybe 120 Watts???), they appear to be useless.

A good start is to measure your power requirements... Get a Kill-a-Watt type meter and plug in your drier. Try it on high and low and see what you need. We need two readings... The Power Usage (Watts--something like 1,500 Watts on high), and the kWH (kilo Watt*Hours)... For example, a 1,500 Watt drier used for 15 minutes would be:

• 1,500 Wattts * 1/4 hour = 375 WH = 3.75 kWH of energy used

Using my "made up numbers" above, a 12 volt battery bank (flooded cell lead acid) would be:

• 1,500 Watts * 400 AH per 1,000 Watts of inverter power = 600 AH @ 12 volt battery bank (minimum)

And based on 2 days of storage and 50% maximum discharge:

• 375 WH * 1/0.85 AC inverter eff * 1/12 volt battery bank * 2 days storage * 1/0.50 maximum discharge = 147 AH @ 12 VDC battery bank (nominal)

So--The size of the battery bank, in this case, is driven by the high power required by the hair drier (Watts). The actual total energy used (Watt*Hours) is actually not that much.

There are other options (AGM and LiFePO4 batteries for example) that can supply higher power for short periods of time--But generally, the overall system requirements will not need those (much more costly) battery types.

Of course, you have other loads in your home, so the battery bank (plus solar) is sized to supply the rest of your loads. I would ask what are your planned loads and system basics (battery bank size, solar array, AC inverter, backup genset?). And, roughly (nearest major city) will the system be installed (sizing for amount of sun you will receive).

Please create your own thread (post here, and I will move this to your own thread). It will make it easier to talk about your specific needs/system design.

-Bill