Enovatek Energy – Hybrid Solar Air Conditioner

DBS Serangoon Gardens is strategically located at Maju Avenue within a residential and shopping district in Singapore. To go green, DBS engaged Enovatek Energy to help them reduce their air-conditioning costs and lower their CO2 emissions, by installing 3 solar AC units to cool their digital lobby. Enovatek Energy identified certain heat loads within the digital lobbyand found that the machinery, such as the Automated Teller Machines (ATMs) and human traffic were the main contributing factors. Enovatek Energy proposed the use of two 18,000 BTU Solar ACs in the lobby and a 9,000 BTU AC unit in the Video Teller Machine (VTM) Room. The Enovatek Energy Hybrid Solar Air Conditioner runs on DC power harvested from solar panels during the day. At night or when there is insufficient sunlight, the air conditioning system switches to conventional AC, the grid. On a cloudy day, the system still draws as much power possible from the sun’s irradiance. Being an intelligent system, the algorithm will always draw as much power possible from renewable resources first and then tap into conventional AC power. The solar air conditioning system operates without inverters, batteries, or controllers. As this was a new project (no replacement of existing air conditioners), Enovatek Energy faced a few key performance indicators:

  1. To keep the room cool 
  2. To increase energy efficiency 
  3. To tap as much solar as allowed to run the air conditioners 

Enovatek Energy opted to use 2 x 18,000 split wall mount solar ACs as cool air would be unilaterally spread across the whole area. As the VTM room was a smaller space, a 9,000 BTU solar AC was installed. This would allowed the room to achieve ambient temperatures – with a low of 18 degrees. Enovatek Energy’s R-32 Solar Air Conditioners are approximately 15% more efficient when run on AC grid compared to big brand invertor air conditioners, because it uses more DC parts. To further increase energy efficiency, Enovatek Energy installed motion sensors into the unit. When there was no human traffic, the AC units would automatically be on standby mode. A challenge faced by Enovatek Energy was with the roof material, and the available space to effectively implement solar PVs. Due to the old structure, flexible solar panels (7kgs) were used instead of conventional solar panels (26kgs) with no racking as to mitigate further weight and roof load issues. Using a BCA approved energy monitoring device, Enovatek Energy collected data from one of the 18,000 BTU split units to help Enovatek Energy and DBS understand the amount of energy used and also its efficiency, regardless either from AC grid or from the solar. The data suggested that Enovatek Energy’s Solar Hybrid Air Conditioning system managed to draw power from the sun for approximately 9 hours in a 24-hour period. In AC mode, the air conditioner did not use more than 1000 watts and used lower power when the outdoor ambient temperature was cooler. Solar power started at approximately 9am until approximately 6pm. Though statistically, it can be said that the Solar Hybrid ACs were using 52% of its power from solar over a 24-hour period, the data is likely to change with the inclusion of motion sensor devices and human traffic once the branch opens. However, it is evident that with the adoption of a solar air conditioner, electricity consumption and CO2 emissions can significantly be reduced by a saving of approximately 50%.