science

Sun-free photovoltaics

Sun-free photovoltaics is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sun-free photovoltaics rather than just read about it. In short: Sun-free photovoltaics is a photovoltaics technology which does not require sunlight to produce electricity. This technique was developed by research team at Massachusetts Institute of Technology.

Key takeaways

Sun-free photovoltaics belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sun-free photovoltaics to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sun-free photovoltaics from memory before moving on to harder problems.

Reference excerpt

Sun-free photovoltaics is a photovoltaics technology which does not require sunlight to produce electricity. This technique was developed by research team at Massachusetts Institute of Technology. Photovoltaic cells convert light to electricity most efficiently at specific wavelengths. The surface features of Sun-free photovoltaics is engineered such that it converts heat energy into the specific wavelengths. This increases the efficiency of existing thermophotovoltaic (TPV) systems.

Principle of working The surface of this material is etched with billions of nanoscale pits, so that it emits wave at the specified wavelengths and suppresses other wavelengths which are not required. When the surface is exposed to heat energy, it radiates light energy at required wavelengths. The atoms liberates free electrons when radiation is applied, thus generating electricity.

Development A device that uses radioisotopes is capable of producing electricity for up to 30 years without interruption using a process called radioactive decay. Another similar device was developed by researchers from MIT, which uses butane as a fuel source. It has the size of a button and is estimated to operate three times longer than a similarly sized lithium-ion battery and has the advantage of recharging immediately upon refuelling. Thermo-photovoltaics, which is a technology developed in the 1960s, is capable of converting heat energy into electricity. It was previously known that sunlight is not absolutely necessary for photovoltaic cells to operate. Infrared radiation is not utilized efficiently in photovoltaic materials which are characterized by low band gap, though the performance is comparatively better than normal silicon photovoltaic cells. One example of photovoltaics utilizing heat is a photovoltaic diode which produces electricity from heat given off by a hydrocarbon fuelled thermal emitter. In Sun-free photovoltaics, the thermal emitter described above is finely tuned to emit specific wavelengths that the photovoltaic diode can utilize, while at the same time stopping the wavelengths that cannot be used by the diode. This is achieved by etching features of nanoscale like ridges and holes on a photonic crystal so that the light passing through the crystal can be modified.

Operation A slab of tungsten is used as a thermal emitter with billions of nanoscale pits on the surface, with each pit acting like a resonator. On heating, specific wavelengths are radiated by the slab as it generates an altered emission spectrum.

Applications Sun-free photovoltaics can be applied in electronic devices like smartphones. Its value of current density has the capability to be tripled in the coming years, when it could power a smartphone for more than 20 days without needing to recharge in between. It can also be used to utilize waste heat from electric appliances like televisions and electronic appliances like mobile phones.

References

Worked examples

Example 1 — a first encounter with Sun-free photovoltaics

Start with the simplest possible case. Write down what Sun-free photovoltaics claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sun-free photovoltaics before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sun-free photovoltaics ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sun-free photovoltaics

In research: Sun-free photovoltaics appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sun-free photovoltaics in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sun-free photovoltaics is common in secondary-school and first-year university syllabi. It links to neighbouring topics Photovoltaics, so understanding it makes those chapters shorter.
In everyday life: Look for Sun-free photovoltaics outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sun-free photovoltaics in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sun-free photovoltaics means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sun-free photovoltaics out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sun-free photovoltaics in simple terms?

Sun-free photovoltaics is a photovoltaics technology which does not require sunlight to produce electricity. This technique was developed by research team at Massachusetts Institute of Technology.

Why does Sun-free photovoltaics matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sun-free photovoltaics?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sun-free photovoltaics.