Hourly Energy Usage Simulation Techniques For Evaluating Digester Gas CHP System Costs and Savings

Combined Heat and Power (CHP) systems are superior to other digester gas utilization systems in their ability to reduce utility costs and carbon emissions. Economic viability of digester gas-fired CHP is a function of many plant specific variables, foremost of which are electric and gas utility rates, building and process heating (and cooling) loads, digester gas impurities, and digester gas production. These and other utility, system, and plant specific data impacts on digester gas energy recovery system economics are presented, discussed, and evaluated using both simple and sophisticated energy modeling techniques including a method of hourly energy calculations.Some noteworthy findings are the greatly superior return on investment, compared to CHP alternatives, of heating-only systems in plants with significant facility heating loads, and the general need for monetary incentives, both capital and operating, to lower economic hurdles to cogeneration implementation.