Sustainable Energy Management: Concentrating Solar Fueled Thermal Processes

This paper includes a conceptual analysis of using a concentrating solar thermal (CST) and biogas system to fuel thermal processes at WWTP as a renewable energy resource. This approach would combine CST, biogas and thermal biosolids processing technologies. By way of example, the paper includes an analysis of a CST fueling a combined heat and power system at 91st Avenue WWTP in Phoenix, AZ – an ideal location for CST technology. The concept includes using anaerobically digested biogas as a supplemental fuel source for the CHP system. The primary heat source would be used for thermal drying of biosolids. There would be enough fuel from CST and biogas to operate steam turbines to supply enough power to meet current demand on an annual basis. Waste heat from the steam turbine would be used for anaerobic digester heating and plant cooling via an absorption chiller. 91st Avenue has examined the potential of biogas fueled CHP and biosolids thermal drying independently; however, 91st Avenue has not examined CST or combining CST, CHP, and thermal drying technologies.Individually, each technology has been well–vetted with many installations globally; however, the technologies have never been used together to the authors' knowledge. The authors believe the combination of technologies to be viable as a fuel source for biosolids thermal processes in areas with high direct radiation, such as the southwestern United States.Many WWTP use fossil-fuel based technologies for thermal processing. CST technologies could either be retrofitted into existing systems or designed as part of new systems. Depending on the amount of heat available and the heat demand of the thermal process, CST could be designed to provide the entire heat demand at all times of the year, or, more likely, would be supplemented when needed with another fuel, such as digester gas or natural gas. Design considerations include:Land availabilityRooftop areaMonthly solar radiation potentialSeasonal solar radiation variationWeatherDrying system heat demandBack-up heating system