reality check

[Stewart Corman]

I have been diddling with my calculator and looking at potential power capability at presumed Cp values/TSR and then comparing to nominal rotation speed for the 2.3KW servo A-B 515E.

Then for the 18 foot turbine design, calculated the total maximum power delivered based upon allowable current ratings. The continous stall current is rated at 6 amps and I will presume only running at half speed ie 1500rpm/230v. This equates to about 4KW when used as a generator. When you work out the resistor loads, it equates to three 1500 watt elements rated at 230v ...fine!
The internal windings are about 3 ohms and the heater loads are about 35ohms ,so only 10% get wasted heating the atmosphere ...fine again!

So, I then wanted to better understand what 4KW of power means?

I installed two nichrome heater elements into the plenum of my forced hot air system. Each is rated at 5KW containing three individual coils making it convenient for three phase loads, whereby the second element can be used in parallel or series to vary the load on the generator for light, nominal, overload (braking) conditions.


I predominately burn firewood as a renewable resource and just about finished 6 full cords for the season.
I have previously determined that at $0.12/KW incremental cost from grid , that fuel oil at $3.80/gal is equivalent cost to electric ( was $2 last season)...don't want to support the Arabs, so I am NOT buying oil !

So I just tried an experiment last night to see what 4KW of heating really does and found out .... NOT much !

Our sleep setting on thermostat is 60F, so I turned off the oil furnace and connected 4KW of nichrome and turned on the forced air blower (1/3hp = 500watts??) for five hours continuous. The temperature outside stayed a bit above freezing all night in mid 30's. I am heating about 1/2 the house or about 1300sqft ...the temp inside just about stayed even in 3 main rooms and two bathrooms got slightly warmer with doors mostly closed. After I turned off the juice, in the next two hours the rooms cooled by only one degree. So at best the 4KW electric was just making up for heat losses in a fairly mild environment. Cost was about $0.50/hr running.

A KW of electric at 100% efficiency is 3,4170 BTU so 4KW/hr = 13.7KBTU, whereas oil delivers 100KBTU/hr, but cycles at 50% duty. So oil delivers 3x the heating vs electric and can heat up the house easily. In cold weather can run continuously, but I have never seen it happen.

For me to use electric (or as backup system), I have to hook up entire 10KW elements and it only heats 1/2 the house at $1.20/hr compared to oil cost at $1.90/hr @50% duty cycle for whole house.

Bottom line ...even an 18 foot turbine will NOT heat your house sufficiently when the wind is blowing at 15mph and temps are below freezing ...forget sub zero...a 10 footer is just a toy unless you have steady 28mph wind.
Heating domestic hot water is viable, but we have figured it to be only $20/mo grid cost and wind isn't reliable ...need to use forced hot air as heat "dump" when domestic water is topped out, and also need a good dump use for summertime when heat is a liability.

BTW, good site for energy consumption comparisons:
http://www.americanenergysystems.com/fuel_comparison.cfm
note: contact in Cortland just told me that corn went from $80/ton last season to $180 now ! firewood cost me $140 last spring
Wood pelts are surprisingly economical, but distributing heat in large house is problematic

Stew Corman from sunny Endicott

[Ralph Day]

Yes Stew, electric heating from renewables not good use of re$ources.

Now, if you take solar heat and use it to heat, it's much more efficient and the payback is supposed to be fairly quick. One trouble is, in the summer you have oodles of sun and no need for it. Maybe someone has an air conditioner that uses concentrated heat to evap the refrigerant...much like a propane refrigerator? A thought for you engineering types.

Ralph

PS what has your snow load been this winter? My scrapings off the pv arrays are almost up to the bottom panel...about 3.5feet so far.

[Stewart Corman]

Ralph,
I have a reasonable amount of passive solar at new end of house addition.
A 6x16 solar room and two full height, 3 pane bay windows facing south west.
When sun is out all day and temps in 40's, house gets up into high 60s and we get thru the night w/o any firewood.
Spring garden is already planted on trays out there, so we open door to house when it gets above 85 degrees. A few cold deepfreeze nights and we bring them inside. Time to start annuals indoors on Sunday. Maybe zukes and cukes?

We have missed most of the snow this season ..been to the North, been to the South, and temps have been fairly mild. Most we had at any one time is only about 10 inches. Used the snowblower twice. Went cross-country skiing only about 5 times.

I had thoughts of doing domestic water preheat with passive solar for summer, but don't want to fool with antifreeze in winter. Will see how turbine comes online for preheating water.

Stew

[Rob Beckers]

Hi Stew,

A few weeks ago I was talking to an RE installer in Newfoundland. He was interested in 25 kW wind turbines, or larger. I asked what he was planning to use those for. The answer was that he installs them at residential houses. Surely something smaller, say around 6 kW, would do fine with the all the wind they have over there I asked, since that size turbine would make well over 1000 kWh/month over there (that's about the average for a Canadian household). The answer was that most people on the island have an all electrical house, including heating, and they use 6000 kWh/month and up. It goes to show what you found out; just how much energy it takes to heat the average house.

The irony of it all is that Newfoundland is a substantial oil producer. Seems they don't use it locally...

-RoB-