With the rapid expansion of the world's population, coupled with the technological developments in large areas of the world, a dramatic increase in the demand for energy in all forms, including fuels and electricity for heating, lighting, transportation and manufacturing processes has been created. The construction of hydroelectric facilities and the development of fossil fuel resources have continued as it has for many years.
It has become increasingly evident, however, that for a number of reasons these efforts are inadequate to keep pace with the demands of the growing population. Furthermore, fossil fuel resources are known to be limited and the use of fossil fuels are also known to have a negative impact on the environment. It is well known, for example, that the burning of fossil creates numerous harmful greenhouse gasses such as carbon dioxide and methane and the like which contribute to global warming. Even further, environmental concerns are seriously impeding the development of new sources of fossil fuels.
Attention has thus tended to focus on other sources of energy such as nuclear and solar. It is well known, however, that nuclear energy carries serious risks of radiation leaks or explosion thereby limiting its use. The more logical source of energy, therefore, is solar. Solar energy is safe, nonpolluting and has the further advantage that it is not depleted with use.
One promising approach for the collection and conversion of solar energy utilizes a field of reflectors known as heliostats focused on a central collector or receiver that is typically mounted at the top of a tower. The collector may contain liquid salt or some other material that is heated by the sun's rays that are focused on the collector by the heliostats. The heated salt is then passed through a heat exchanger for generating steam that can be used to power a turbine for generating electricity. Alternatively, steam can be generated directly in the collector which functions essentially as a boiler like device. Solar steam generators of these types can be seen, for example, in U.S. Pat. Nos. 8,365,529 and 6,957,536 that issued to Litwin et al. in 2013 and 2005, respectively.
Because the earth moves relative to the sun during the day and from day to day throughout the seasons, the heliostats are normally mounted on pedestals using a gimbal mechanism which enables them to be tilted and turned to follow the sun from early morning to late afternoon each day. All of the heliostats in the reflector field are moved in a manner taught, for example, in U.S. Pat. No. 4,832,002 that issued to Medina in 1989.
In a typical solar energy system discussed above wherein the solar receiver is utilized in conjunction with a plurality heliostats, a loss of coolant to the solar receiver due to a coolant pump failure (or due to some other failure) requires that the reflectors be automatically and rapidly defocused to prevent receiver melt down. However, a pump failure is frequently associated with an overall power failure which would also prevent automatic defocusing of the reflectors. In that type of power failure, receiver melt down would occur.
U.S. Pat. No. 4,380,229 that issued to Glasgow in 1983 attempts to solve this problem by providing a protection means wherein an automatic flow of sufficient coolant will occur to prevent receiver melt down until the reflectors become defocused with respect to the solar receiver due to the earth's rotation. This has the effect of shutting down the steam generation used to operate the turbine, subsequently, halting the generation of electricity. Furthermore, it may take substantial time to get the system up and running again.
Because the prior art has not proven to be totally satisfactory, a need exists for a solar power generator which does not rely on the use of a coolant to prevent melt down and which can continuously operate without fear of the receiver overheating or melting down.