Civil Engineering Reference
In-Depth Information
4
Utility Plants and Renewable Sources
4.1
Introduction
Energy is transported to the site as purchased fuel (oil, gasoil, LPG, natural gas,
etc.) or as electricity purchased from utilities. Water, to which attention must be
paid when an energy management program is implemented, can be either purchased
from utility or pumped from wells.
In addition, energy can be used from the so-called renewable sources, i.e., waste
recovery and permanent natural power sources such as sun, wind, geothermal,
wave—tidal and ocean thermal energy, and water. The importance of these
power sources, which are mainly transformed in electricity, depends on their
geographical location, distance from main networks, and the operating period that
generally does not exceed 2,500 h/year.
4.2
Utility Plants and Renewable Sources, from
Input Energy to End Users
Utility plants, mainly producing electric energy and heat, may be classified as fossil
fuel or nuclear plants. In some local conditions, utility plants use other sources,
namely hydro—geothermal—solar concentration—wind.
Utility plants generally use steam-condensing turbines, gas turbines, and com-
bined cycles. Heat recovery for district heating is a common way to improve overall
efficiency; of course local regulations, climatic conditions, and plant location
determine the attractiveness of this possibility.
As a general rule, utility plants' efficiency ranges between 35 and 60 %; if
electric distribution losses are considered, an average value of 33-57 %
can be assumed for the overall efficiency from primary energy to end
users. This means that 0.15-0.24 kg of equivalent oil is required to deliver
1 kWh to the end user.
