COGENERATION – KILLING MANY BIRDS WITH ONE STONE
Steam is very powerful. It does not only run an engine but also possesses the ability of air conditioning besides its various uses. Diesel and/or gas generators not only produce electrical power but may also produce steam which may be used for heating or cooling. This is like killing many birds with one stone. Technically, this is known as Cogeneration.
Cogeneration, also known as Combined Heat and Power (CHP), is the on-site production of multiple types of energy — usually electricity, heat and/or cooling — from a single source of fuel. Cogeneration replaces the traditional methods of acquiring energy, such as:
- Purchasing electricity from the power grid like Karachi Electric (KE) or WAPDA
- Separately burning natural gas or oil in a furnace to produce heat or steam.
- Using the resultant steam to produce air conditioning through vapor absorption cycle.
The traditional method of purchasing electric energy from a utility is very inefficient and wastes almost 75 percent of the energy in the original fuel due to production and transportation (transmission) losses.
Typically, the energy balance is as under:
- Energy input – 100%
- Energy wasted in generation – 60%
- Energy wasted in transmission – 10 to 15%
- Energy delivered as electrical output – 30%
On-site cogeneration systems convert 70 percent to 90 percent of the energy in the fuel that is burned into useful electricity or heat.
Let’s try to understand which power generation installations are the most suitable for cogeneration. Almost any facility with a simultaneous need for both electric and thermal energy is a potential candidate for the energy saving benefits of cogeneration- that is, on-site systems that produce both electric power and thermal energy from a single source of fuel. Ask yourself the following questions and if the answers to all are “yes”, then your facility may be a good candidate for a cogeneration application.
- Is the electrical load of your facility consistently greater than 1,000 kW?
Note: Facilities with larger energy needs can generate larger savings and have a shorter payback period.
- Is the thermal load of your facility equal to 1 million Btu / hour or more?
(a) This could take the form of hot water, an absorption chiller load, low-pressure steam — or a combination of all three.
- s the duration of your simultaneous need for heating/cooling and electric power greater than 4,000 hours per year
- Is the cost of electricity significantly higher than cost of natural gas?
(a) Greater the differential between the price of electricity and the price of natural gas (equivalent Btu basis), greater the likelihood of savings.
- Is reliability of electric service a major economic concern?
(a) For many commercial and industrial facilities, a power outage can be very costly. On-site cogeneration systems, when designed properly — offer significantly better reliability than local utilities. They are less vulnerable to vandalism and transformer or transmission line failures, and, with proper maintenance, will offer decades of reliable operation.