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Better heat exchangers for concentrated solar power

Solar thermal systems are a good example of the particle-wave dualism expressed in Planck’s constant h: E = hf. Where h is the Planck constant, f is the frequency of the light and E is the resulting energy. Thus, the higher the frequency of the light, the higher the amount of energy. Solar thermal metal collectors transform the energy of high-frequency light by generating them to an abundance of low-frequencies through Compton shifts. Glass or ceramic coatings with high visible and UV transmittance absorb the low frequency light generated by the metal because they effectively absorb infrared light (so-called heat blockers). The efficiency of the solar thermal system improves significantly with increasing size, which is also the biggest advantage of such systems compared to photovoltaic generators. One disadvantage, however, is the downstream transformation of heat into electricity with the help of heat exchangers and turbines − a problem not only in solar thermal systems.

To provide the hot gas (supercritical CO2) to the turbines, heat exchangers are necessary. These heat exchangers transfer the heat energy generated by a power plant to the working fluid in a heat engine (usually a steam turbine) that converts the heat into mechanical energy. Then, the mechanical energy is used to generate electricity. These heat exchangers are operated at ~800 Kelvin and could be more efficient if the temperature were at >1,000 Kelvin. The entire process of converting heat into electricity is called a power cycle and is a critical process in power generation by solar thermal plants. Obviously, heat exchangers are pivotal elements in this process.

Ceramics are a great material material for heat exchanger because they can withstand extreme temperature fluctuations. However, unlike metals, ceramics are not easy to shape. Relatively coarse shapes, in turn, are made quickly and easily. In contrast, metals can be easily formed and have a high mechanical strength. Metals and ceramics have been valued for centuries for their distinctive properties. For example, bronze and iron have good impact resistance and are so malleable that they have been made into complex shapes such as weapons and locks. Ceramics, like those used to make pottery, have been formed into simpler shapes. Their resistance to heat and corrosion made ceramics a valued material. A new composite of metal and ceramic (a so-called cermet) combines these properties in amazing ways. A research group led by Mario Caccia reported now in the prestigious journal Nature about a cermet with properties that makes it usable for heat exchangers in solar thermal systems.

The history of such composites goes back to the middle of the 20th century. The advent of jet engines has created a need for materials with high resistance to heat and oxidation. On top of that, they had to deal with rapid temperature changes. Their excellent mechanical strength, which often surpassed that of existing metals, was highly appreciated by the newly created aerospace industry. Not surprisingly, the US Air Force funded more research into the production of cermets. Cermets have since been developed for multiple applications, but in most cases have been used for small parts or surfaces. The newly released composite withstands extreme temperatures, high pressures and rapid temperature changes. It could increase the efficiency of heat exchangers in solar thermal systems by 20%.

To produce the composite, the authors first produced a precursor, which was subject to further processing, comparable to potting the unfired version of a clay pot. The authors compacted tungsten carbide powder into the approximate shape of the desired article (the heat exchanger) and heated it at 1,400 °C for 2 minutes to bond the parts together. They then further processed this porous preform to produce the desired final shape.

Next, the authors heated the preform in a chemically reducing atmosphere (a mixture of 4% hydrogen in argon) at 1,100 °C. At the same temperature, they immersed the preform in a tank of liquid zirconium and copper (Zr2Cu). Finally, the preform was removed by heating to 1,350 °C. In this process, the zirconium displaces the tungsten from the tungsten carbide, producing zirconium carbide (ZrC) as well as tungsten and copper. The liquid copper is displaced from the ZrC matrix as the material solidifies. The final object consists of ~58% ZrC ceramic and ~36% tungsten metal with small amounts of tungsten carbide and copper. The beauty of the method is that the porous preform is converted into a non-porous ZrC / tungsten composite of the same dimensions. The total volume change is about 1-2%.

The elegant manufacturing process is complemented by the robustness of the final product. At 800 °C, the ZrC / tungsten cermet conducts heat 2 to 3 times better than nickel based iron alloys. Such alloys are currently used in high-temperature heat exchangers. In addition to the improved thermal conductivity, the mechanical strength of the ZrC / tungsten composite is also higher than that of nickel alloys. The mechanical properties are not affected by temperatures of up to 800 ° C, even if the material has previously been subjected to heating, e.g. for cooling cycles between room temperature and 800 °C. In contrast, iron alloys, e.g. stainless steels, and nickel alloys loose at least 80% of their strength.

(Photo: Wikipedia)

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What is the need of renewable energy sources?

Currently, we are using coal, oil, and gas as our energy resource. They are known as fossil fuels and when burned, they release heat energy that can be turned into electricity. Unfortunately, they cannot be replenished. This form of energy can also be harmful for the health and also a degrading factor for the entire health of the world. People today are turning towards the use of renewable energy for it is an energy source that is less harmful for the environment and for our health.

There are different renewable sources of energy in use today like solar, wind, and hydroelectric power. Wind turbines and solar panels are becoming an increasingly common sight to be used as energy resource. Some of the other forms of clean energies are geothermal, and energy from biomass. These are effective solutions for avoiding, minimizing, and mitigating the use of fossil fuels.

Here are the best benefits of a renewable energy source –

It ensures less global warming

Different human activities are overloading the atmosphere with various harmful gases and other emissions. These gases act like a blanket that result in a web of significant harmful impacts. Increasing the supply of renewable energy would allows the replacement of carbon intensive energy sources with to reduce green house gas emissions.

It improves the public health

Air pollution from using coal and oil is linked with breathing problems, heart attacks, cancer and neurological damage. Most of the negative impacts come from the air and water pollution. Wind, solar, and hydroelectric systems will generate electricity with no associated air pollution emissions.

It is better to use the inexhaustible energy

Strong winds, sunny skies, heat from underground water, and abundant plant matter will provide constant supply of energy. Renewable energy provides a significant share of electric needs, even after accounting for potential constraints.

There are many of economic benefits

Renewable energy is supporting thousands of jobs. Solar panels need workers to install them; wind farms need technicians for maintenance.

There are a lot of reasons for moving towards the use of renewable energy for now and in the future. But there are some limitations also with the use of such energy resources. It is thus advisable to contact the support experts of professionals dealing with the use of green house gases for energy production.

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Go Green! Be part of the world experiencing a renewable energy revolution

There are a lot of benefits to choosing green energy for day-to-day energy production. Mof course, there are the environmental benefits that come with the use of renewable energy. Choosing green energy helps to reduce carbon emissions and air pollution. It also offers a number of social and economic benefits that are often overlooked.

It is the need of the hour to quickly adopt green energies for protecting our environment. Developed countries are slowly and steadily taking the initiative towards green energy consumption. While hydro power is the oldest form of green renewable production, the two best known forms of green energy are wind and solar. Their prices are falling dramatically, as we reported previously, and it is expected that the price will go down more significantly in the coming decades.

Here are some of the many benefits of green energy –

There will be less service disruption

Despite their intermittency, green energy services are more reliable thansome traditional energy services if implemented in smart grids. This because they can be used in decentralized grids. These decentralized energy systems are less likely to experience large-scale failure if they are distributed properly.

More jobs are created with green energy

There is a rise in appreciation and technological development of green energy. It will lead to the creation of more jobs in the renewable energy industry. In the U.S. there are already more people employed in the green energy sector than in conventional energy production. Naturally, such jobs are always local and cannot be transferred to other countries. Globally, there are almost 10 million people employed in the green energy sector.

Going green results in lower healthcare costs

The use of fossil fuels is resulting in air and water pollution, leading to cancer & breathing problems, heart attacks, and other serious health issues. Replacing fossil fuels by green energy sources will help reduce the harmful emissions.

Green energy will result in a stronger economy

The green services do more for the community as most of the jobs in the renewable energy sector are created locally. These services power homes efficiently and local governments collect taxes from renewable energy projects, which is used to improve public services.

How businesses benefit from renewable energy?

Enterprises or business always thrive for new ways to be more sustainable. Going green help the company’s bottom line and also attract new clients & customers. Switching to renewable energy brings many different benefits to a business. For one, there are bigger rewards for the business for switching to more sustainable energy sources because they save on their energy bills. Energy forms like solar energy provide the opportunity to cut the energy costs while contributing to the Earth’s health. Solar panels are harvesting energy from the sun which, resource that is accessible to everyone and therefore an intelligent investment for the businesses.

Companies can save a substantial amount on their energy bills by going green. The savings can rage to thousands to dollars depending on the business size. Moreover, if renewable energy is combined with energy storage such as batteries or power-to-gas, businesses can become grid independent which protects from disasters and blackouts.

All of these benefits come do not just cut energy spending but also protect the environment. Global warming is has real and serious consequences for our planet, but if we continue to practice our business as usual our future generations will have to pay up for our deeds.

Conclusion: Renewable energy is bringing many different benefits to business who profit immensely. If are you looking for a way to leave a smaller footprint on the planet, switch to renewable energy options and save money. When businesses show that they care for the health of their clients, it is more likely for the clients to products or services.