Co-generation is a solution that provides electricity by combusting gas and uses the heat generated in the process to provide air-conditioning, distillation, or heating solutions in a simultaneous manner.
Co-generation or CHP (Combined Heat and Power) is simultaneous production of double or triple energy from a single fuel source burnt in a prime mover. Depending on the extent of exhaust heat utilisation, the overall efficiency can extend over 85 per cent, thereby improving efficiency, environment friendliness, and returns. This simply equates to the fact that co-generation based power plants supply electricity and air conditioning or heating solutions from a single unit of fuel consumed while other energy solutions would only generate electricity.
The prime mover could be a gas turbine or reciprocating engine. Cogeneration or tri-generation application is pronounced in process industries such as petrochemical, fertilizer, pharmaceuticals, chemical, paper, textile, ceramic, and automotive factories to name a few. It is also successfully installed to power commercial establishments such as malls, offices, IT parks, data centres, airports, and hospitals. Some of the advantages of this technology are: cogeneration has a higher fuel efficiency usage when compared with other non renewable sources of energy. With efficiency reaching 85 per cent, CHP Solution is the most efficient power generation option, resulting in optimized utilization of scarce resources of fossil fuels. Cogeneration produces just 1/3rd the amount of greenhouse gas emissions to that of a pure power plant. It also reduces transmission and distribution (T&D) losses since energy is generated at site. This would amount to 10 per cent of power being saved by an IPP. Cogeneration also brings more reliability and flexibility to the power transmission network as excess power can be transferred to the grid seamlessly.
As a case study to highlight the efficacy of co-generation or CHP-based solutions we can use the typical power requirement of a multipurpose shopping complex and how co-generation fares viz-a-viz conventional board line power.
A typical mall that is about 1,056,000 sq.ft in area would require uninterrupted energy for 12 peak hours from 10 am to 10 pm with a high chilling requirement to the tune of 500 TR. The power demand would be close to around 1,400 kW
Being a mall with different shop outlets, including dining, hypermarket, banquet, multiplex, apparel stores, it would have a high reactive power consumption resulting in low power factor electricity demand
Being a commercial establishment for whom grid tariffs are in the highest bracket, and also due to above factors, the developer would receive a hefty energy bill
The energy expenditure for such an establishment could be reduced by installing a cogeneration power plant that is designed to the configuration of 1.4 MW gas engine with suitable 390 TR VAM (vapour absorption machine). The hot jacket water and exhaust of gas engine is utilised to produce chilled water through VAM
The net tariff for commercial establishments in Mumbai from grid is at Rs.14/Kwh. The gas cost per unit comes to about Rs.9/Kwh. The capex cost of installation is Rs.1.75/Kwh and misc. costs of 1Rs./Kwh. With chilling provided free of cost in this cogeneration solution, there is accrued benefit of Rs.2.5/Kwh to owner. Hence, the net electricity generation cost comes to Rs.9.25/Kwh. This means there is net saving of Rs.4.75/Kwh*
Apart from being a cost effective option for replacing board line electricity, Co-generation can also be used as an effective backup power option in places where gas transmission lines are available. Cogeneration plants can be fired by biogas, or industrial and municipal organic waste. CHP plants utilise waste gas as the fuel for electricity and heat generation.
Waste gases can be gas from animal waste, landfill gas, gas from coal mines, sewage gas, and combustible industrial waste gas. If explored diligently by local governing bodies´ cogeneration could answer one of the most pressing challenges of our times, i.e. effective waste management solutions.
Author: Rajesh Shah, President, Sterling and Wilson Cogeneration Power Solutions