Marketing Scoops: Moon Dust Converted To Solar Cells Could Power Space Exploration

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Researchers have successfully created solar cells from simulated moon dust that could fuel power. The cells the scientists developed should convert sunlight into energy efficiently and withstand radiation damage, they report in the Cell Press journal Device. The technique kills two space logistics birds with one stone: it could create electricity without involving heavy payloads……..Continue reading….

By Paul Smaglik

Source: Discover Magazine

Critics:

A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.^[1] It is a type of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as “solar panels”.

Almost all commercial PV cells consist of crystalline silicon, with a market share of 95%. Cadmium telluride thin-film solar cells account for the remainder. The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.

Photovoltaic cells may operate under sunlight or artificial light. In addition to producing solar power, they can be used as a photodetector (for example infrared detectors), to detect light or other electromagnetic radiation near the visible light range; also to measure light intensity.

The operation of a PV cell requires three basic attributes:

The absorption of light, generating excitons (bound electron-hole pairs), unbound electron-hole pairs (via excitons), or plasmons.
The separation of charge carriers of opposite types.
The separate extraction of those carriers to an external circuit.

There are multiple input factors that affect the output power of solar cells such as temperature, material properties, weather conditions, solar irradiance and more. A similar type of “photoelectrolytic cell” (photoelectrochemical cell), can refer to devices

using light to excite electrons that can further be transported by a semiconductor which delivers the energy (like that explored by Edmond Becquerel and implemented in modern dye-sensitized solar cells)
using light to split water directly into hydrogen and oxygen which can further be used in power generation
direct heat as a “solar thermal module” or “solar hot water panel”

Arrays of solar cells are used to make solar modules that generate a usable amount of direct current (DC) from sunlight. Strings of solar modules create a solar array to generate solar power using solar energy, many times using an inverter to convert the solar power to alternating current (AC). Solar cells were first used in a prominent application when they were proposed and flown on the Vanguard satellite in 1958, as an alternative power source to the primary battery power source.

By adding cells to the outside of the body, the mission time could be extended with no major changes to the spacecraft or its power systems. In 1959 the United States launched Explorer 6, featuring large wing-shaped solar arrays, which became a common feature in satellites. These arrays consisted of 9600 Hoffman solar cells.

By the 1960s, solar cells were (and still are) the main power source for most Earth orbiting satellites and a number of probes into the solar system, since they offered the best power-to-weight ratio. The success of the space solar power market drove the development of higher efficiencies in solar cells, due to limited other power options and the desire for the best possible cells, up until the National Science Foundation “Research Applied to National Needs” program began to push development of solar cells for terrestrial applications.

In the early 1990s the technology used for space solar cells diverged from the silicon technology used by terrestrial panels, with the spacecraft application shifting to gallium arsenide-based III-V semiconductor materials, which then evolved into the modern III-V multijunction photovoltaic cell used on spacecraft that are lightweight, compact, flexible, and highly efficient.

State of the art technology implemented on satellites uses multi-junction photovoltaic cells, which are composed of different p–n junctions with varying bandgaps in order to utilize a wider spectrum of the sun’s energy. Space solar cells additionally diverged from the protective layer used by terrestrial panels, with space applications using flexible laminate layers.

Additionally, large satellites require the use of large solar arrays to produce electricity. These solar arrays need to be broken down to fit in the geometric constraints of the launch vehicle the satellite travels on before being injected into orbit. Historically, solar cells on satellites consisted of several small terrestrial panels folded together. These small panels would be unfolded into a large panel after the satellite is deployed in its orbit.

Newer satellites aim to use flexible rollable solar arrays that are very lightweight and can be packed into a very small volume. The smaller size and weight of these flexible arrays drastically decreases the overall cost of launching a satellite due to the direct relationship between payload weight and launch cost of a launch vehicle.

In 2020, the US Naval Research Laboratory conducted its first test of solar power generation in a satellite, the Photovoltaic Radio-frequency Antenna Module (PRAM) experiment aboard the Boeing X-37. Research into solar power for terrestrial applications became prominent with the U.S. National Science Foundation’s Advanced Solar Energy Research and Development Division within the “Research Applied to National Needs” program, which ran from 1969 to 1977, and funded research on developing solar power for ground electrical power systems.

A 1973 conference, the “Cherry Hill Conference”, set forth the technology goals required to achieve this goal and outlined an ambitious project for achieving them, kicking off an applied research program that would be ongoing for several decades.The program was eventually taken over by the Energy Research and Development Administration (ERDA), which was later merged into the U.S. Department of Energy.

Following the 1973 oil crisis, oil companies used their higher profits to start (or buy) solar firms, and were for decades the largest producers. Exxon, ARCO, Shell, Amoco (later purchased by BP) and Mobil all had major solar divisions during the 1970s and 1980s. Technology companies also participated, including General Electric, Motorola, IBM, Tyco and RCA.

Solar cells are typically named after the semiconducting material of which they are composed. These materials have varying characteristics to absorb optimal available sunlight spectrum. Some cells are designed to handle sunlight that reaches the Earth’s surface, while others are optimized for use in space.

Solar cells can be made of a single layer of light-absorbing material (single-junction) or use multiple physical configurations (multi-junctions) to take advantage of various absorption and charge separation mechanisms. Solar cells can be classified into first, second and third generation:

First generation cells—also called conventional, traditional or wafer-based cells—are made of crystalline silicon, the commercially predominant PV technology, that includes materials such as polysilicon and monocrystalline silicon.
Second generation cells are thin film solar cells, that include amorphous silicon, CdTe and CIGS cells and are commercially significant in utility-scale photovoltaic power stations, building integrated photovoltaics or in small stand-alone power system.
Third generation of solar cells includes a number of thin-film technologies often described as emerging photovoltaics—most of them have not yet been commercially applied and are still in the research or development phase. Many use organic materials, often organometallic compounds as well as inorganic substances. Despite the fact that their efficiencies had been low and the stability of the absorber material was often too short for commercial applications, there is research into these technologies as they promise to achieve the goal of producing low-cost, high-efficiency solar cells.

As of 2016, the most popular and efficient solar cells were those made from thin wafers of silicon which are also the oldest solar cell technology. By far, the most prevalent bulk material for solar cells is crystalline silicon (c-Si), also known as “solar grade silicon”. Bulk silicon is separated into multiple categories according to crystallinity and crystal size in the resulting ingot, ribbon or wafer. These cells are entirely based around the concept of a p–n junction. Solar cells made of c-Si are made from wafers between 160 and 240 micrometers thick.

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