Methodology development and assessment of lower carbon industrial process heat through solar energy and heat pumps

The reduction of energy consumption in industrial processes, notably within low temperature industries, leads to greater economic gain and lower carbon emissions. Numerous energy audits and case studies within the food and beverage industry suggest that initial efforts to reduce energy consumption should focus on energy efficiency measures such as heat recovery and process optimization due to their lower cost of implementation. Eventually, however, an efficiency limit is reached and the only way to further reduce thermal energy consumption and carbon emissions is by implementing renewable heat solutions. Three technologies are of main interest: solar thermal collectors, photovoltaics, and vapor compression heat pumps. To determine their feasibility for low-temperature (< 150 °C) industries, solar thermal and photovoltaic process heat plants are simulated under numerous boundary conditions, elucidating their specific energy yield potential as a function of technology type, process and ambient temperature, and annual solar irradiation. The negative effect of process load and profile, thermal storage size, and facility outages on annual specific yield is also considered in this work. An assessment methodology is developed that compares solar thermal against three other technology couplings (direct-resistance photovoltaic heating, grid and photovoltaic powered heat pumps), determining the lower cost heat generation or carbon abatement technology. The methodology is designed to be near-universally applicable and highly flexible, allowing for variations in geographical location, process temperature, production schedule, and both present and predicted future technology investment. In nearly all cases, the methodology has a model prediction error of less than 5% (root-mean-square). Results indicate that, at current conditions, solar thermal produces lower cost process heat than direct-resistance photovoltaics in most cases, excluding processes above 100 °C in regions with limited solar irradiation. Grid and photovoltaic powered heat pumps produce lower cost heat when operating for the majority of the year but become the more expensive renewable heat technology when operating less than 1000 hours annually. To abate carbon, solar thermal is the clear choice unless a heat pump has access to very low carbon electricity, primarily from nuclear or renewable sources. In the near future, photovoltaic and heat pump capital investments are expected to decrease. In turn, solar thermal must drive down costs to safeguard its vital role in the renewable energy future. Using the developed methodology, solar thermal should conservatively target turn-key plant investments of no greater than 200 €/m2ap in lower solar irradiation regions and 300 €/m2ap in higher solar irradiation regions to protection itself against other competing renewable heat technologies.