7AC Technologies, Inc.
Air conditioning is a very large contributor to U.S. and world energy consumption. Heating and cooling costs for commercial and industrial buildings exceed 25 percent of U.S. primary energy consumption (cooling alone accounts for 4.5 Quads out of 40 Quads) and typically accounts for almost half of a building’s operating costs. Air conditioning is also a significant cause of grid instability with cycling compressor motors turning on and off, and causing load issues on hot summer days. Conventional air conditioners improve efficiency only marginally every year and retrofitting older rooftop units does not result in significant energy savings.
Conventional AC units use a lot of power for dehumidification rather than sensible cooling. 7AC’s Liquid Desiccant Air Conditioner (LDAC) systems lower the operating costs of commercial buildings for heating and cooling by 50 to 75 percent by using a strong saline solution (a desiccant) for moisture removal. A waste heat source can then be used to re-concentrate the desiccant. The LDAC unit seamlessly replaces existing rooftop HVAC systems and has less than a 1 year payback period when powered with natural gas or with a small conventional chiller. When waste heat is used (e.g. from Solar Thermal, Industrial processes or the rear of PV modules), heating and cooling costs reduce to essentially zero with a payback period of much less than one year, excluding the cost of the thermal delivery system.
The initial costs for the 7AC LDAC are very similar to a conventional HVAC system. Replacing an HVAC unit happens every 15 years on average and first costs are very important in the decision process. The 7AC LDAC has however a much lower energy consumption and since an HVAC unit’s annual energy costs are almost the same as the cost of a new unit, the payback period of the LDAC system is usually measured in months. This will help building owners to pro-actively replace their older HVAC units, rather than waiting for them to fail. It also enables Energy Service’s Companies (ESCOs) to carry LDAC products as part of an energy retrofit.
The 7AC liquid desiccant technology works by simultaneously dehumidifying and cooling incoming air. In a conventional HVC system, air is cooled to the saturation point and overcooled so that the moisture is removed to the desired humidity level. The air is then often reheated so that it enters the space at a comfortable temperature. Liquid desiccant systems have been installed for many years, but suffer from two disadvantages: they heat the air as it is being dried since it is usually an adiabatic process, and they have risk of desiccant getting airborne and transported into the building, which can lead to corrosion issues. The 7AC membrane plates simultaneously cool and dry the air and the membrane (licensed from NREL) prevents any of the desiccant from becoming airborne. Simultaneous cooling and dehumidification is a significantly more efficient process. This approach saves between 50 and 75 percent of energy as compared to a conventional HVAC.
7AC’s 10-ton LDAC removes the annual Green House Gas (GHG) equivalent to that of 2 cars, and double that if supplemented with a waste heat system. If 10% of the global market used LDAC technology, this would remove 22 million metric tons of GHG or 3.7 million cars annually.