Out with the old (over complicated, expensive solar). In with the new (better and more efficient solar at lower cost).
Case in point: the Minneapolis- St. Paul international Airport’s cutting-edge solar thermal system with a new innovative design approach.
Two decades ago, conventional solar called for installing a water heater or, for larger systems, a boiler that heated a tank. Later, solar morphed into separate, individual components that drew heated water into the water heater storage only if someone washed their hands. This design suffers from too much heat loss, and the solar can’t heat the water heaters to prevent them from firing. Preheating is now an outdated and inefficient design.
The new design we’re sharing today integrates the drainback tank and storage tank, reducing costs and components. At the Minneapolis-St.Paul airport, the engineering firm of Michaud, Cooley & Erickson did this with great finesse and accuracy. All 152 collectors charge the storage tank. Because the storage tank is a huge drainback tank, no energy is left to waste in a separate individual drainback vessel. That cost is eliminated too.
Conventional designs use a heat exchanger to transfer the solar BTUs into the storage devise. Any time you launder BTUs through a heat exchanger, you’ll pay an efficiency penalty. Store the pure energy until it is needed, and then use a heat exchanger to deliver it to the needed source.