Carnot cycle systems are high efficient systems. They have work specific characteristics that make them distinguished from other thermodynamics systems such as Brighton, Rankin and sterling cycle based systems and can be used as a cost-effective solution.
Reversed Carnot cycle is the best option for heating and cooling of residential compounds and buildings compared to other conventional systems such as fossil fuel and electric heaters.
The performance of every heating system is described by a coefficient called Coefficient of Performance or Cop. CoP is a measure of heating energy that is entered into a building in return for the electrical energy consumed. For heating systems, this coefficient is defined as
As can be seen, the less the difference between the cold reservoir and the hot source, the higher is the COP. In most cases, with a good design, it is possible to obtain COP=4 which is a high figure compared to other heating systems with maximum 60% efficiency. Literally, COP=4 means that the energy usage in these systems is ¼ the of the energy created by an electric element for the same performance.
However, Carnot cycle has its own restrictions and deficiencies in using in cold regions. The main problem is that the outer unit or the evaporator that is located out of the compound and has the duty of pumping heating energy into the building can freeze in a cold weather conditions, disturbing the whole system. In order to resolve this issue there are some feasible solutions. Burying the evaporator deep in the ground can resolve the issue. Due to the low thermal conductivity of the ground and earth’s huge mass, the ground temperature at a depth of 15ft with the temperature on the surface differs 6 month. This means that any temperature at the surface of the earth takes a six month time to be transferred deep into the depth of 15ft inside the ground. As a result the coldest temperature at the depth of 15 ft happens in summer time. This poses a good condition to resolve the problem of freezing of the evaporator.
Of course, this solution is not a simple and practical one, since it has its own problems and challenges including the corrosion of pipes, finding a practical way for transferring the heat up to the compound, possibility of servicing and maintenance of the system and finally and the most important one digging of the ground to place the evaporator at such a depth.
In the coming articles, practical solutions along with related calculations aimed at resolving these challenges are going to be discussed so that this solution can be practically implemented.