Integrating solar hot water on the Big Island

Solar hot water Horizon Guest House Big Island Hawaii

The Big Island is known for sun, surf and adventure. Here on the Kona Coast we have an abundance of sunny days that make it the perfect location to install solar panels. Horizon B&B has integrated solar hot water to help reduce the cost of heating water by electricity. This system is simple to implement and low-maintenance.

Domestic solar hot water supply

The Horizon Guest House domestic hot water supply is supplemented by a separate solar system. First installed over twenty-five years ago, the solar panels are all located in positions to best maximize the power of the sun.

There are two solar panels located next to the vegetable garden. Water is pumped from the house to the solar panels whenever the sensors on the panels detect that the temperature of the panels is greater than the temperature of the hot water heater in the house. When this occurs the pump system is activated. The water is circulated out to the panels, heated, and then sent back to the house.

Delta-T thermostat on the hot water heater

Swimming pool solar hot water

The solar system is also used to heat the swimming pool water. A larger bank of panels is located on the hillside below the pool. On sunny days, the sun heats a sensor near the pool. This sensor compares the temperature of the water in the pool with that of the temperature of the panels. When there’s enough temperature difference between the two, a valve opens and water is sent to the solar panels to heat the pool. When the sun goes away, the sensor cools and it automatically shuts the valve.

Solar hot water Horizon

Guest wing solar hot water supply

There is a separate bank of solar panels to heat the domestic water supply for the guest wing. These panels are located on the hillside below guest room number 4. When the sensor heats to a certain level, the water is circulated to the panels.  

The sensor on all three banks of solar panels will activate the circulation of water when the temperature difference reaches 15 degrees. For example, if the temperature in the hot water heater is 127 degrees then the temperature in the solar panels needs to reach 142 degrees before the valve will open and the water is sent out. We have set the hot water heater to switch to electric only when it goes below 110 degrees. As a safety precaution the temperature shut-off is 160 degrees. This is to avoid sending water that would simply be too hot back to the water heater. The water sent to the water heater remains at temperature for 2-3 days due to the water heater being well-insulated.

Solar hot water helps heat our outside shower

The solar hot water system has been a great way to utilize the power of the sun to help heat the water needed to run the bed and breakfast. These systems are relatively easy to install and the differential temperature thermostat is key to integrating solar panels with a standard electric hot water heater.

Further reading:

In 2010 it was mandated that solar water heaters be complusory on all new single-family homes constructed in Hawaii.

https://www.cleanenergyauthority.com/solar-energy-news/solar-hot-water-heaters-mandatory-in-hawaii

 

 

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