Solar energy can be used in space cooling in hotels. This is achieved with the use of specific solar panels – evacuated tube solar collectors – which can generate hot water at around 120 oC. The hot water is used afterwards for cooling production via evaporation cooling through thermal absorption systems. The hot water causes the evaporation of fluids with low boiling point at low temperatures and cold water is produced.
In August 2016, the USA-based energy company Energy Concepts started up a solar-heated Helisorber chiller to demonstrate the use of air conditioning and simultaneous production of heat-pumped hot water at a hotel in California. Concentrating flat plate collectors traded under the name Chromasun make up the solar field partly powering the unit. The Helisorber has been designed to meet domestic hot water demand for the hotel’s guest rooms and kitchen and covers some of the cooling load required for the large building.
The first-of-its-kind cooling project at the hotel in California includes a Helisorber with a capacity of 25 tons of refrigeration. According to design parameters, this unit named HS25 runs on solar heat at 250 °F (121 °C) supplied by a solar field with a thermal capacity of 500,000 BTUs (147 kW). Hot water storage at a capacity of 3,000 gallons (11,356 lit) helps smooth out operation during the day, since hot water demand in the hotel is highly variable. A natural gas standby system ensures uninterrupted heat supply. On a sunny day, about 30 % of the heat input for the Helisorber unit comes from solar energy.
One excellent source of heat is solar thermal, especially with new efficient, low-cost evacuated tube collectors. Hot water heat output amounts to 880,000 BTUs (258 kW) per hour at 130 °F (54 °C). The chilling co-product is 25 tons at 44 °F (6.7 °C). All of the heat supplied by the HS25 goes to heating domestic hot water, so that a cooling tower is not needed and only four small pumps require electricity.
The cost of installing the demonstration plant has been covered by the California Energy Commission (CEC) and local utility Sempra, which has to reduce energy consumption and peaks by funding energy efficiency measures. The installation was carried out by California-based solar thermal system integrator Adroit Energy and the cooling specialists at Retrofit Technology. The solar field was delivered by Chromasun, a San Francisco-based collector manufacturer that stopped production shortly after the solar field at the hotel was commissioned. Energy Concepts partnered with Chromasun for the project to develop specifications, design the control, monitoring and data acquisition systems and optimize servicing and performance.