A successful Distributed Generation (DG) installation is all about finding the thermal load. Although self-evident to all engineers and planners of large and small Combined Heat and Power (CHP), this fact is much more pertinent to the small-scale (<250 kW) generators whose customers often face a high investment capital for equipment and installation ($/kW). Today, this is the world of conventional microturbines which, by and large, have struggled to achieve the Return on Investment (ROI) desired by DG users, and thus must rely on government financial incentives to continue in business.
While attention has been focused on engineering more energy efficient microturbines – with power conversion of 30% LHV – the physics and limitations of turbine materials and fabrication are such that efficiencies can never approach those of larger industrial or utility turbines. If that is the case, then microturbines must have lower turnkey cost, greater reliability, and greater value-added use of their waste heat than today’s commercial units to reach broader CHP market adoption. This is a fundamental shift that requires a new and innovative approach.
Leva Energy has taken this approach by emphasizing the thermal needs of the customer, first, while providing the lowest cost electricity for an attractive ROI. We must further ask ourselves “what is the heat recovery method for microturbine exhaust that offers the greatest value-added use of that waste heat?” While conventional “integrated” microturbine CHP systems carry their own post-recuperator heat exchangers capable of producing hot water in small quantities, this lower temperature waste heat recovery often fixes the power/heat ratio, and offers low or no thermal load flexibility. Although adequate for niche markets that use low quantities of 140 F water, such systems are also limited to overall CHP efficiencies of 65-70%, or lower in cases where the integrated hot water boiler is bypassed to meet lower demand. Steam generation and higher demand hot water systems that require backup burners, instead, provide much higher overall CHP efficiencies (80-85% HHV) with variable thermal load, and often requiring much less expensive microturbines with a much higher power conversion efficiencies approaching 90% (HHV).
