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A PV diagram plots the change in pressure P with respect to volume V for some process or processes. Typically in thermodynamics, the set of processes forms a cycle, so that upon completion of the cycle there has been no net change in state of the system; i.e. the device returns to the starting pressure and volume.
Solar potential in the Czech Republic Solar panels in Prague. The Czech Republic had almost two gigawatts (GW) of photovoltaic capacity at the end of 2010, but installed less than 10 megawatts (MW) in 2011 due to the feed-in tariff being reduced by 25%, after installing almost 1,500 MW the year before.
This Process Path is a straight horizontal line from state one to state two on a P-V diagram. Figure 2. It is often valuable to calculate the work done in a process. The work done in a process is the area beneath the process path on a P-V diagram. Figure 2 If the process is isobaric, then the work done on the piston is easily calculated.
Figure 1: A Carnot cycle illustrated on a PV diagram to illustrate the work done. Figure 2: A Carnot cycle acting as a heat engine, illustrated on a temperature-entropy diagram. The cycle takes place between a hot reservoir at temperature T H and a cold reservoir at temperature T C. The vertical axis is temperature, the horizontal axis is entropy.
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially used for electricity generation and as photosensors.
English: A cyclic thermodynamic process described on a pressure-volume diagram. A and C are constant-pressure (isobar) evolutions, B and D are constant-volume (isochoric) evolutions. A and C are constant-pressure (isobar) evolutions, B and D are constant-volume (isochoric) evolutions.
The PV diagram is a particularly useful visualization of a quasi-static process, because the area under the curve of a process is the amount of work done by the system during that process. Thus work is considered to be a process variable , as its exact value depends on the particular path taken between the start and end points of the process.
The discontinuity in , and other properties, e.g. internal energy, , and entropy,, of the substance, is called a first order phase transition. [12] [13] In order to specify the unique experimentally observed pressure, (), at which it occurs another thermodynamic condition is required, for from Fig.1 it could clearly occur for any pressure in the range .