Combined heat and power systems (CHP) are an energy efficient way for refineries to generate power, allowing for greater independence from grid operations and even the potential to export power to the grid. This can increase reliability of supply and cost-effectiveness, depending on the regulations in the state where the refinery is located.
The Benefits of CHP
CHP systems are significantly more efficient than standard power plants because they take advantage of what would otherwise be losses in conventional power plants by utilizing waste heat. In addition, transportation losses are minimized when CHP systems are located at or near the refinery. Third party companies may also be used to install and operate CHP systems, reducing capital expenditures but still gaining the benefits of a more energy efficient system of heat and electricity supply.
Optimizing CHP Operation
Optimizing the operation strategy of CHP units and boilers is an area in which additional savings can be achieved. The development of a dispatch optimization program to meet steam and electricity demand can lead to significant energy and cost-savings.
Combining CHP and Absorption Cooling
For systems requiring cooling, absorption cooling can be combined with CHP to use waste heat to produce cooling power. This could reduce the amount of electricity used for cooling by up to 6%.
Innovative Gas Turbine Technologies
Innovative gas turbine technologies can make CHP more attractive for sites with large variations in heat demand. Steam injected gas turbines (STIG or Cheng cycle) can absorb excess steam, for example due to seasonal reduced heating needs, to boost power production by injecting the steam in the turbine. STIGs have been installed at over 50 sites worldwide and are found in a range of industries and applications.
Steam Turbines
Steam turbines are often used as part of the CHP system in a refinery or as stand-alone systems for power generation. The efficiency of the steam turbine is determined by the inlet steam pressure and temperature as well as the outlet pressure. Each turbine is designed for a certain steam inlet pressure and temperature and operators should make sure that the steam inlet temperature and pressure are optimal.
CHP in Large and Small Refineries
Large refineries may install large CHP systems of up to 525 MW, and third party companies may carry the total investment of $250 million. Small refineries may also benefit from CHP, with a 6.5 MWe gas turbine CHP unit resulting in annual energy savings of $3.8 million and a payback period of about 2.5 years.
Conclusion
CHP systems offer refineries an energy efficient way to generate power, allowing for greater independence from grid operations and even the potential to export power to the grid. This can increase reliability of supply and cost-effectiveness, depending on the regulations in the state where the refinery is located. In addition, CHP can be optimized for maximum efficiency and combined with absorption cooling for further energy savings. Innovative gas turbine technologies can also make CHP more attractive for sites with large variations in heat demand. CHP is an attractive option for both large and small refineries, with the potential for significant energy and cost-savings.