Eco & Eco Absorption Chiller

09 14th, 2009

With the SorTech Absorption Chiller S 08 and S 15 offered by Eco & Eco it is now possible, for the first time, to cheaply produce cold from thermal driving energy, even at a low power range.
Everywhere that solar heat, waste heat, and district heat, for example, are available, an alternative that is more environmentally friendly and cheaper to operate than conventional compression chillers is likewise available. The combination of this with combined heat and power plants – and then as power heat-cold coupling – is a viable option for generating cold from already occurring and insufficiently usable heat applying as little electrical energy as possible.
An important advantage of ACS, compared to absorption chillers, is its high power and high degree of efficiency at very low driving temperatures – starting at 60°C. This is of significant importance, particularly when it comes to solar cooling, because cooling can also be guaranteed with inexpensive flat-plate collectors, even with moderate solar radiation. Because, as far as the cooling process is concerned, the ACS contains so few moving parts susceptible to wear and tear, maintenance of the unit is limited to an annual inspection and restoration of the vacuum in the unit’s interior as well as cleaning of the re-cooler lamellae. This can be done during maintenance of other building equipment and thus does not incur any additional costs worth mentioning.

1.) What is the main difference between the absorption chiller ACS and absorption chillers?

Contrary to absorption technology, where only fluid agents are employed and transferred, the working principle behind the ACS is solid state sorption – or absorption. Here a solid agent (silica gel) is used which is not in constant but periodic contact with the evaporating refrigerant. In this manner, neither “cold production” nor hot water usage is constant. By combining two absorber modules a quasi-continuous operation is achieved which is marked by periodic temperature fluctuations. The occurrence of such fluctuations is undesirable in certain applications and must, therefore, be smoothened with the help of buffers, etc. This disadvantage, however, is offset by the fact that fluids do not need to be pumped; hence, there is no need for moving parts. In addition, due to the usage of silica gel as the active agent the ACS is able to work easily, even at very low driving temperatures. This is where absorption-based cooling technology is limited, requiring driving temperatures of at least 80°C.

The four process chambers are connected to each other by internal, automatically-functioning steam valves. These valves influence the directional flow of the evaporated refrigerant into adsorber chamber 1 or 2 and the condenser, depending on the phase of the process. In operating phase 1, hot water passes through adsorber 1. The refrigerant, which has accumulated
on the inner surface of the silica gel, is expelled, thus causing it to condense on the cooled condenser. The condensation heat emitted is removed through the re-cooling circuit. The condenser has a constantly low temperature and pressure level and, therefore, acts as a temperature reducer. Simultaneously, adsorber 2 adsorbs (i.e. water vapor is “sucked” from the evaporator and bound in the silica gel). During the conversion of the state of aggregation from a liquid to a gas, energy is extracted from the refrigerant which passes through the evaporator – enthalpy of evaporation. During adsorption of the water vapor in the silica gel, adsorption heat is released. This heat is also removed through the re-cooling circuit of the ACS. Through the external condensate return the refrigerant liquefied in the condenser is recirculated into the evaporator. As a result of the cyclical change of adsorption and desorption (i.e. from the “production of cold” and regeneration in both adsorber chambers), it is possible to achieve quasi continuous operation.