Calculation
of the quantity of energy provided by the system of autonomous renewable energy supply
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Wind generator power supply quantity
To calculate the wind generator power capacity we use this formula
where N – power capacity (kW); S = πR 2 – rotor rotation area, where R – blade length (in our case R = 12 m); ρ – air density, ρ = 1,02 kg/m3 ; ξ – wind utilization factor, we consider it 0,5; V – wind speed, m/sec.
The average wind speed according to the wind map in Massachussets is 4m/sec on 10 m height. It is common knowledge that the speed of wind depends on height of the rotor wheel over the ground level. To calculate the wind speed at the rotor wheel level we use this formula
where V0 – known speed of wind at the height H0 = 10 м; H – wind generator tower height (in our case 35 m); V – estimated wind speed; а – empiric index of degree equal to 0,14;
The forecasting wind speed at 35 m height is:
therefore power capacity of the rotor wheel is:
Total annual energy production, E taking in to account the electric generator efficiency coefficient η = 0,8 ,will be
(7,5 mWt per month)
However, assuming the inertia of the system, as well as technological stops for servicing the wind generator, we reduce the expected amount of electricity per year to 50 MWh. or 4.2 MWh per month. The volume of the produced electric energy is more than enough to supply condominium for 4 families. The excessive surplus of electricity is transformed into heat energy by heat pump.
One must burn 20000 liters of diesel fuel to produce such an amount of electric energy by means of electric generator.
One must burn 20000 liters of diesel fuel to produce such an amount of electric energy by means of electric generator.
The quantity of energy collecte by the solar collectors
where Wc – average annual solar energy falling daily per square meter (3 kW for MA); η – solar collector efficiency coefficient – 0,8; Sс – solar collectors area (basic set is 40 m 2 ). Therefore: ФОРМУЛА MW·h which is equal to the amount of heat energy produced by diesel heater burning 3500 liters of diesel fuel
Therefore:
MW·h
which is equal to the amount of heat energy produced by diesel heater burning 3500 liters of diesel fuel.
The effectivity of renewable energy supply is reasonable to compare with diesel generators or heaters, because they are the only traditional energy suppliers that can operate without connection to the grid or pipelines, otherwise we have to take into account the cost of their laying. The total annual amount of energy produced by autonomous renewable energy supply system equals to the amount that could be produced by the burning at least 33,5 metric tons of diesel fuel.
The effectivity of renewable energy supply is reasonable to compare with diesel generators or heaters, because they are the only traditional energy suppliers that can operate without connection to the grid or pipelines, otherwise we have to take into account the cost of their laying. The total annual amount of energy produced by autonomous renewable energy supply system equals to the amount that could be produced by the burning at least 33,5 metric tons of diesel fuel.
