Solar Thermal Integration With and Without Energy Storage: The Cases of Bioethanol and a Dairy Plant

This paper looks at the resulting combination of working fluid inlet temperature and heat storage capacity as a means for increasing the solar fraction and the number of hours that renewable energy can be supplied to a background process. The portion of the process heat duty that can effectively be supplied from solar thermal energy, or solar fraction, increases with the inlet temperature of the solar field. The increase of inlet temperature is beneficial since it reduces the size of the solar field. The way to achieve higher inlet temperatures is by means of surplus heat that is stored during sunny hour. For further increasing the period of operation beyond sunny hours, thermal storage must be increased. In this work, two case studies are considered and it is found that the integration of solar thermal plants proves to be a cost-effective alternative in energy conservation and pollution reduction. The payback time reveals that doubling the time where the solar system delivers the required temperature is still profitable.