Photovoltaic thermal hybrid solar collector Photovoltaic thermal hybrid solar collector Photovoltaic thermal hybrid solar collectors, also known as hybrid PV/T (PVT) or solar cogeneration systems, are power generation technologies that convert solar radiation into usable thermal and electrical energy. Such systems combine a solar cell, which converts sunlight into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the PV module. These technologies can be more energy efficient overall than solar photovoltaic (PV) or solar thermal alone. Significant research has gone into developing a diverse range of PV/T technologies since the 1970s.. While many collector types have been
Galois module Z), as can be deduced from the theory of Gaussian periods (the Hilbert–Speiser theorem). On the other hand the Gaussian field does not. This is an example of a "necessary" condition found by Emmy Noether ("perhaps known earlier?"). What matters here is "tame" ramification. In terms of the discriminant "D" of "L", and taking still "K" = Q, no prime "p" must divide "D" to the power "p". Then Noether's theorem states that tame ramification is necessary and sufficient for "O" to be a projective module over Z["G"]. It is certainly therefore necessary for it to be a "free" module.