WIND ENERGY SYSTEMS - Cd3wd

Chapter 7—Asynchronous Loads 7–48
(d) Would you anticipate any problem in clustering the necessary number of turbines at
a pumping station and making the mechanical connections between wind turbines
and pumps and between pumps and necessary piping? Discuss.
7. A wind turbine manufacturer is offering for sale a 12 m diameter propeller mechanically
connected to a Jacuzzi type FL6 centrifugal pump through a 12:1 gearbox. You have
an application where large amounts of water need to be pumped against a head of 80 ft
and this system could be used to reduce energy consumption by other pumps which are
electrically driven. The wind characteristics are described by the Weibull characteristics
k =2.2andc = 7.5 m/s. Water starts to flow with a pump power input of 8.5 bhp.
Pump power input has to be limited to 35 bhp because of cavitation problems. The
turbine efficiency is assumed to be a constant value of 0.32 over the operating range
between cut-in and rated wind speeds. The pump efficiency averages about 0.8 under
all operating conditions.
(a) What is the cut-in wind speed?
(b) What is the rated wind speed?
(c) How much water will the system pump in a year? Express result in both gallons
and m 3 .
8. A paddle wheel water heater has dimensions L = 0.07, w = 0.07, b = 0.038, D =0.6,H
=0.4,andd = 0.2 m, as defined in Fig. 8. The wheel is turning at a rotational speed
of 4500 r/min. What is the power being converted into heat?
9. You install a 40-kW wind turbine on your farm. The rate structures are such that the
utility will pay you a much better price for your excess generation if you can guarantee
to supply them 10 kW during a 4 hour peak each day. You allow for two calm days in
a row and decide on a 80-kWh battery bank with inverter. The 6-V lead-acid batteries
have a base that is 0.18 m by 0.26 m. A total of 80 batteries are required, in two banks
of 40 batteries each to get the necessary 240 V required by the inverter.
(a) How big an area is required to store the batteries if they are to be in a single layer?
Include space for access to the batteries and space between batteries for cooling.
Justify your assumptions.
(b) Battery efficiency is 0.85 during both charge and discharge. What is the rated
current of each 6 V battery during discharge?
(c) Is battery cooling a problem? Discuss.
10. You are designing a cogeneration power plant for an apartment building. Available fuels
include No. 1 diesel at $1.70 per gallon, ethyl alcohol at $1.40 per gallon, and methyl
alcohol at $1.30 per gallon. Each fuel is used at the same overall efficiency. Which fuel
is the most economical choice, if efficiencies and capital costs are the same in all cases?
Wind Energy Systems by Dr. Gary L. Johnson November 21, 2001