Tri-generation Plant
● India will need to build 700-900 million square meters of commercial and residential space every year up until 2030 to meet the needs of a booming urban populace. Energy demand just for this sector is anticipated to rise by at least four times in this time frame.
● The demand for energy in India, the world's fastest growing major economy, is set to rise substantially as the country invests in infrastructure, urbanisation, and industrialisation. The rise in disposable income will also create a greater demand for energy services such as cooling, heating, and lighting. According to BP Energy Outlook, India's share of global energy demand is Projected to rise to 11 percent in 2040 from 5 percent in 2016. The International Energy Agency, in its India Energy Outlook 2015, predicted that the country's energy use will more than double by 2040, reaching 1,900 million tones of oil equivalent.
● As part of its nationally determined contributions, India has committed to reducing the emissions intensity of its gross domestic product by 33 to 35 percent by 2030 from 2005 level. Therefore, it becomes important to meet the rising energy demand with sustainable alternatives.
Need of Tri-generation Plant:
● Tri-generation deals with the study of simultaneous generation of electricity and useful heating and cooling from the combustion of a biomass fuel or a solar heat collector.
● Conventional coal or nuclear-powered power stations convert only about 33% of their input heat to in electricity. The remaining 67% emerges from the no turbines as low-grade waste heat with no significant local uses so it is usually rejected to the environment.
● In a tri-generation system, the supply of high temperature heat first drives a gas or steam turbine powered generator and the resulting low temperature waste heat is then used for water or space heating.
● Such systems can attain higher overall efficiencies than cogeneration or traditional power plants, and provide significant financial and environmental benefits. Tri-generation systems can play a vital role in reducing energy requirements.
● Large-scale, low-carbon, and cost-effective solutions are hence necessary for addressing this sector's energy needs.
● We have identified tri-generation as such a viable alternative: with the advantage of simultaneously providing reliable power, heating and cooling supply using clean fuel, wide spread adoption of this technology could significantly transform India's energy landscape.
● By extension, tri-generation could hence significantly reduce the electricity load of buildings without compromising commercial activity and electricity grid stability.
● Tri-generation is the next step of cogeneration that is the residual heat available from a cogeneration system is further utilized to operate refrigeration cycle.
Definition of Tri-generation
Tri-generation is defined as the production of electricity in the simultaneous process of cooling, heating and power generation from only one fuel input in the one process.
● Typically, gas-fired generators are used to produce electricity. The by-product is waste heat, which is then directed to absorption chillers and boilers for space cooling, hot water and related purposes.
● India's growing access to natural gas, a typical input for tri-generation systems and the cleanest burning hydrocarbon, will greatly enable wider adoption of tri generation.
● The combination of distributed generation of power and utilization of waste heat can provide a sustainable solution to meet the high demand for refrigeration in the region.
● A vapor absorption refrigeration system to produce cooling, the resulting device thus facilitates combined heat power and cooling from a single fuel input.
● The heat produced by cogeneration can be delivered through various mediums, including warm water e.g., for space heating and hot water systems, steam or hot air e.g., for commercial and industrial uses.
Opportunities of Tri-generation :
● Tri-generation technology is a transformative cost effective solution that enables localised, reliable and stable power supply, using a single fuel.
● This technology has been successful in international markets in enhancing operating efficiency of an industrial application by at least 60 %, saving industries and institutions 30-40 % in operating energy costs and reducing greenhouse gas emissions by up to 30 % due to inherent efficiencies in energy generation.
● The technology has direct relevance to hotels, hospitals, airports, retail, office and integrated residential/ commercial complexes that require all forms of building energy simultaneously.
● At 60-80 % efficiency, tri-generation systems, which can use natural gas as fuel, are highly efficient and can be installed, started and stopped quickly. While in a conventional power system, about 70 % of the energy gets wasted in the process of conversion of the fuel into electricity, transmission and distribution, a tri generation system ensures that bulk of these losses are recovered as useful energy.
● Tri-generation systems will especially benefit one of India's most energy-intense industries buildings, which annually constitute over 30 % of the total electricity consumed in India annually. The gross electricity consumption in residential buildings, which in turn consume 75 % of all electricity consumed by all buildings in India, is projected to rise to 600-900 TWh by 2030.
● The demand for air-conditioning, heating and electricity in these buildings and large institutions can be met by installing tri-generation systems that not only generate energy savings but also reduce carbon emissions.
● Residential complexes, and large commercial establishments, therefore, must adopt gas-based tri generation to ensure simultaneous generation of power, heating and cooling while saving on their electricity bills and carbon emission.
● A market assessment study on gas-based tri-generation and co-generation systems in India, prepared by Development Environergy Services Ltd, revealed that the exist unconstrained market potential for tri de generation in the building and industrial sector combined is 15,000 MW. The study, prepared for Energy Efficiency Services Ltd, stated that the market potential is projected around 30,000 MW in the next five years.
● However, the current installed capacity in India is less than 1,000 MW and operating capacity is no more than half of this.
Tri-generation Systems :
Tri-generation systems supply energy in three forms:
1. Electricity
2. Heat
3. Chilled water
Absorption chillers provide an economical and environmental alternative to conventional refrigeration. Combining efficiency, low emission power generation equipment with absorption chillers allows for maximum total fuel efficiency, elimination of harmful refrigerants and reduced overall air emissions. There are a number of different configurations of CHP units where refrigeration can be derived. These include:
◆ Absorption Chillers
◆ Operation using hot water
◆ Operation using steam
◆ Utilization of direct heat through combustion
Tri-generation system for Absorption Refrigeration System :
● Combining a CHP or cogeneration plant with an absorption refrigeration system allows utilisation of seasonal excess heat for cooling. The hot water from the cooling circuit of the plant serves as drive energy for the absorption chiller.
● The hot exhaust gas from the gas engine can also be used as an heat energy source for steam generation to generate the steam from water in boiler, then this is expanded in turbine generating electricity. Also the exhaust steam condensed in condenser rejecting latent heat.
● The cooling circuit hot water passes through the generator of absorption refrigeration system rejecting the heat to working refrigerant then this refrigerant reject heat in condenser and also absorbed the heat from cooling substance providing cooling effect in the working space. So here the utilisation as an energy source for a highly efficient, double-effect steam chiller. Up to 80% of the thermal output of the cogeneration plant is thereby converted to chilled water.
● In this way, the year round capacity utilisation and the overall efficiency of the cogeneration plant can be increased significantly.
Advantages of Tri-generation over Conventional Refrigeration and air conditioning system :
Absorption based refrigeration technology have economic solution for reduced emission, air conditioning systems.
1. Vapour Absorption refrigeration system operated with external heat supply this utilising relatively inexpensive 'excessive heat energy'.
2. Production of electricity that can be fed into the power grid or used to cover the plant's electricity requirements.
3. During winter seasons, the heat energy can be utilised to cover heat requirements.
4. Absorption evaporator called chillers have no moving parts, there for there is no wear and maintenance costs are low.
5. Absorption system has noiseless operation.
6. Low operating costs and life cycle costs.
7. Using water as a refrigerant replaces the use of ozone damaging substances.
Advantages of a Tri-Generation System
1. Savings on energy costs :
Using tri-generation to produce electricity, and specifically when using gas to run the generator and produce heat for the absorption chiller instead of power from the grid to run the air conditioning plant, savings on energy costs in the order of up to 30% can be achieved, depending on the relative price of gas and electricity to the site.
2. Savings on Greenhouse gases:
Producing electricity on site using gas produces approximately 30% less greenhouse gases then using power from the grid in NSW for an equal amount of power output.
3. Back-up power to the site :
A tri-generation plant can provide a substantial proportion of a site's power and in the case of a black out can provide a proportion of the site's energy requirements.
4. Independence from the Grid:
Installing a tri-generation plant provides a site with a level of independence from the power grid. In some areas the capacity of the grid is constrained and in extreme conditions the grid may need to impose resitrictions on use.
5. Constraints on the Grid:
At some sites the grid constraints may be limited or the cost to the user to upgrade the grid so high that the use of the site is constrained. A tri-generation plant can overcome this constraint.
6. Energy costs are rising :
Worldwide the cost of energy from the grid is rising and will continued to rise into the foreseeable future. A tri-generation plant can be a buffer against some of this increase in energy costs.
7. Low payback period :
Recent audits for trigeneration potential projects in India identified payback period on trigeneration integration in industrial applications to be as little as 2 3 years.
8. Buffer against electricity cost and outages :
Using captive generation from gas-based trigeneration instead of electricity buffers industrial consumers against unforeseen spikes in electricity cost. As a relatively independent energy source, it can provide a reliable level of back-up power especially in critical applications, such as hospitals.
9. Replacing thermal energy:
Using natural gas replaces dependence on coal, while nullifying the need for additional energy inputs for heat and cooling generation. Trigeneration systems can hence reduce an establishment's greenhouse gas emissions by up to 50%.
10. Energy efficiency:
Trigeneration plants enable up to 80% of primary energy to reach end use, as opposed to only 25% in conventional power plants. And, producing electricity on-site minimizes transmission losses from grid sourced electricity.
11. Environmentally sustainable :
Absorption chillers commonly use water or ammonia as a refrigerant, making trigeneration-based cooling a zero Ozone Depleting Potential and Global Warming Potential system.
