Thermophotovoltaics: a potential pathway to high efficiency concentrated solar power

Abstract

A high temperature thermophotovoltaic (TPV) system is modeled and its system level performance is assessed in the context of concentrated solar power (CSP) with thermal energy storage (TES). The model includes treatment of the emitter and the heat transfer fluid that draws thermal energy from the TES, which then allows for identification and prioritization of the most important TPV cell/module level properties that should be optimized to achieve maximum performance. The upper limiting efficiency for an idealized system is then calculated, which shows that TPV with TES may one day have the potential to become competitive with combined cycle turbines, but could also offer other advantages that would give CSP an advantage over fossil based alternatives. The system concept is enabled by the usage of liquid metal as a high temperature heat transfer and TES fluid. The system concept combines the great economic advantages of TES with the potential for low cost and high performance derived from TPV cells fabricated on reusable substrates, with a high reflectivity back reflector for photon recycling.

Thermal energy grid storage using multi-junction photovoltaics

“…A type of absorption loss also occurs at the system level and results from the free carrier absorption of sub-bandgap photons, either at the BSR or in the semiconductor itself. The BSR should be designed to be as reflective as possible, so that the unusable sub-bandgap photons are reflected back to the thermal emitter to keep it hot, which is a critically enabling feature for this system concept 30 . A reflectivity of at least 98%, as illustrated in gray in Fig.…”

“…However, while their initial predictions for the cell efficiency are theoretically justified, they do not accurately capture the realistic voltage losses that tend to occur in real cells. Thus, a more realistic consideration of practical cell losses would drive the system towards operation at much higher temperatures than their initial work indicated 30 , as will be discussed in more detail in the next section. Nonetheless, the MPV cells considered herein are still envisioned to incorporate a BSR, but for this temperature regime, higher band gap materials as well as multiple junctions are expected to be optimal.…”

“…Arrow direction and length indicates NPV. The colored contour represents the RTE to break even, assuming 10% IRR,30 year system, and 10 hours of storage.…”

Exploring the potential of a hybrid device combining solar water heating and molecular solar thermal energy storage

“…This has led to the consideration and development of hybrid systems, as for example combined solar thermal and photovoltaic devices. [5][6][7][8] As photovoltaics is finding more and more widespread use, technologies for mitigating challenges with intermittency and load-levelling are becoming increasingly important. In addition to electrochemical (battery) technologies, methods for storage of solar energy in chemical bonds is an attractive option since the chemical energy can be stored in a very compact way.…”

Selection of wetted media for pre-cooling of air entering natural draft dry cooling towers

“…Electricity is then generated by an electric generator which is driven by a steam turbine with the efficiency limited by the Carnot cycle [1]. Considerable research efforts have been conducted to improve the efficiency of the CSP system and make the cost of electricity comparable to that of the conventional fossil-fuel power plant, e.g., thermal energy storage [2,3], thermophotovoltaic heat engine [4] and even the natural draft dry cooling towers (NDDCTs) [5]. The current study focuses on the performance improvement of NDDCTs which may offer the only effective alternative as most CSPs are located in arid or semi-arid areas.…”