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Multistage Sound Wave Engine Used To Develop Innovative Refrigerator



Fridge by francois schnell via flickr

A refrigerator powered solely by waste heat that forms sound waves in a multistage travelling wave thermoacoustic engine, has been developed by Shinya Hasegawa and colleagues at Tokai university.

The refrigerator produced the gas oscillations and refrigeration at a temperature lower than the boiling point of water and achieved a minimum cold temperature of -107.4 °C when the hot temperature was 270 °C. The findings are published in the journal of Applied Thermal Engineering, November 2016.

The operation of thermoacoustic (TA) engines is based on the heating, cooling and oscillation of acoustic (sound) waves created by the thermal expansion and contraction of gases such as helium enclosed dedicated cavities. The potential of TA engines for generating clean and renewable energy was demonstrated in seminal reports published in the late 1990s and early 2000s by researchers in the USA. Notably, these reports into the modern implementations of TA engines have led to increased worldwide research on the development of high efficiency TA engines to convert heat into useful power.

Two of the main hurdles to the proliferation of this technology are (1) high efficiency systems operable at less than 300 °C as compared to the 400 to 600 °C range at the moment; and (2) robust design so that the systems could be used in a wide range of environments such as fishing boats and heavy industries.

Hasegawa and colleagues have designed a high efficiency multistage-type thermoacoustic (MS-TA) engine, without moving parts, that operates at less than 300 oC; the temperature of more than 80% of industrial waste heat. The design of the MS-TA engine was based on finite element numerical analysis conducted by Hasegawa and his group.

Background and aims

“TA engines do not have moving parts, are easy to maintain, potentially high efficiency, and low cost,” says Shinya Hasegawa, an associate professor at the Department of Prime Mover Engineering, Tokai University, Hiratsuka, Japan. “My goals in this research are to develop TA engines that operates at less than 300 oC with more that 30% efficiency, and also to demonstrate a refrigerator operating at -200 oC at these low temperatures.”

Double loop travelling wave thermoacoustic refrigerator (TWTR)

The TWTR consists of three etched stainless steel mesh regenerators installed at optimal positions (“close to the sweet spot”) within the prime mover loop and one fixed in the refrigerator loop. This configuration was designed to trigger thermoacoustic oscillations at lower temperatures and yield a refrigerator temperature of less than -100 oC.

The diameters of the regenerators ranged between 0.2 to 0.3 mm and their lengths were 30 to 120 mm, depending on location. Furthermore, the TWTR had heat exchangers in the form of parallel plates of copper (1.0 mm thick and 27.0 in length) with a 2.0 mm gap.

The thermoacoustic energy conversion of this design is determined by two factors: the ratio of the diameter of the flow channel and thermal penetration depth, and the phase difference between the pressure and cross-sectional mean velocity.

The overall performance of the TWTR system is expressed in terms of the coefficient of performance (COP) and given by the ratio of the cooling power to the total input heating power, that is, the sum of the heating power of each engine.


The COP increased as the temperature of the heat exchangers in the primer loop was increased and the maximum value of COP was 0.029 at 260 °C, and  the corresponding cooling power was 35.6 W.

Furthermore, the researchers obtained gas oscillations at 85 °C —that is lower than the boiling point of water—thereby opening up possibilities for applications of this technology for refrigeration and power generation using low temperature waste heat in factories and automobile engines. Also, refrigeration (−42.3 °C) was achieved at reached 90 °C.

Importantly, the efficiency of the Tokai University TA engine was 18% at minus 107 °C.


“The installment of multiple regenerators in vicinity of the ‘sweet spot’ of the prime mover loop is a major advance in traveling-wave TA engines,” says Hasegawa. “This configuration reduces the temperature for TA oscillations and improves cooling performance.”

Following the successful development of the prototype system reported ion this paper, the next step in this research at Tokai University is the development of practical TA engines with emphasis on contributing to environmental problems.



Are the UK Governments Plans for the Energy Sector Smart?



The revolution in the energy sector marches on, wind turbines and solar panels are harnessing more renewable energy than ever before – so where is it all leading?

The UK government have recently announced plans to modernise the way we produce, store and use electricity. And, if realised, the plans could be just the thing to bring the energy sector in line with 21st century technology and ideologies.

Central to the plans is an initiative that will see smart meters installed in homes and businesses the length and breadth of the country – and their aim? To create an environment where electricity can be managed more efficiently.

The news has prompted some speculation about how energy suppliers will react and many are predicting a price war. This could benefit consumers of electricity and investors, many of whom may be looking to make a profit by trading energy company shares online using platforms such as Oanda – but the potential for good news doesn’t end there.

Introducing New Technology

The plan, titled Smart Systems and Flexibility is being rolled out in the hope that it will have a positive impact in three core areas.

  • To offer consumers greater control by making smart meters available for all homes and businesses by 2020. Energy users will be able to monitor, control and record the amount of energy they use.
  • Incentivise energy suppliers to change the manner in which they buy electricity, to offer more smart tariffs and more off-peak periods for energy consumption.
  • Introduce new standards for electrical appliances – it is hoped that the new wave of appliances will recognise when electricity is at its cheapest and at its most expensive and respond accordingly.

How the Plans Will Affect Solar Energy

Around 7 million houses in the UK have solar panels and the government say that their plan will benefit them as they will be able to store electricity on batteries. The stored energy can then be used by the household and excess energy can be exported to the national grid – in this instance lower tariffs or even payment for the excess energy will bring down annual costs significantly.

The rate of return on energy exported to the national grid is currently between 6% and 10%, but there are many variables to take into account, such as, the cost of battery storage and light levels. Still, those with state-of-the-art solar electricity systems could end up with an annual profit after selling their excess energy.

The Internet of Things

Much of what the plans set out to achieve are linked to the now ubiquitous “internet of things” – where, for example, appliances and heating systems are connected to the internet in order to make them function more smartly.

Companies like Hive have already made great inroads into this type of technology, but the road that the government plans are heading down, will, potentially, go much further -blockchain technology looms and has already proved to be a game changer in the world of currency.

Blockchain Technology

It has already been suggested that the peer to peer selling of energy and exporting it to the national grid may eventually be done using blockchain technology.

“The blockchain is an incorruptible digital ledger of economic transactions that can be programmed to record not just financial transactions but virtually everything of value.”

Don and Alex Tapscott, Blockchain Revolution (2016)

The upshot of the government’s plans for the revolution of the energy sector, is that technology will play an indelible role in making it more efficient, more flexible and ultimately more sustainable.

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4 Case Studies on the Benefits of Solar Energy




Demand for solar energy is growing at a surprising rate. New figures from SolarPower Europe show that solar energy production has risen 50% since the summer of 2016.

However, many people are still skeptical of the benefits of solar energy.Does it actually make a significant reduction in our carbon footprint? Is it actually cost-effective for the company over the long-run?

A number of case studies have been conducted, which indicate solar energy can be enormously beneficial. Here are some of the most compelling studies on the subject.

1.     Boulder Nissan

When you think of companies that leverage solar power, car dealerships probably aren’t the first ones that come to mind. However, Boulder Nissan is highly committed to promoting green energy. They worked with Independent Power Systems to setup a number of solar cells. Here were the results:

  • Boulder Nissan has reduced coal generated electricity by 65%.
  • They are on track to run on 100% renewable energy within the next 13 years.
  • Boulder Nissan reduced CO2 emissions by 416,000 lbs. within the first year after installing their solar panels.

This is one of the most impressive solar energy case studies a small business has published in recent years. It shows that even small companies in rural communities can make a major difference by adapting solar energy.

2.     Valley Electric Association

In 2015, the Valley Electric Association (VEA) created an 80-acre solar garden. Before retiring from the legislature, U.S. Senate Minority Leader Harry Reid praised the new project as a way to make the state more energy dependent and reduce our carbon footprint.

“This facility will provide its customers with the opportunity to purchase 100 percent of their electricity from clean energy produced in Nevada,” Reid told reporters with the Pahrump Valley Times. “That’s a step forward for the Silver State, but it also proves that utilities can work with customers to provide clean renewable energy that they demand.”

The solar energy that VEA produced was drastically higher than anyone would have predicted. SolarWorld estimates that the solar garden created 32,680,000 kwh every year, which was enough to power nearly 4,000 homes.

This was a major undertaking for a purple state, which may inspire their peers throughout the Midwest to develop solar gardens of their own. It will reduce dependency on the electric grid, which is a problem for many remote states in the central part of the country.

3.     Las Vegas Casinos

A number of Las Vegas casinos have started investing in solar panels over the last couple of years. The Guardian reports that many of these casinos have cut costs considerably. Some of them are even selling the energy back to the grid.

“It’s no accident that we put the array on top of a conference center. This is good business for us,” Cindy Ortega, chief sustainability officer at MGM Resorts told Guardian reporters. “We are looking at leaving the power system, and one of the reasons for that is we can procure more renewable energy on the open market.”

There have been many benefits for casinos using solar energy. They are some of the most energy-intensive institutions in the world, so this has helped them become much more cost-effective. It also helps minimize disruptions to their customers learning online keno strategies in the event of any problems with the electric grid.

4.     Boston College

Boston College has been committed to many green initiatives over the years. A group of researchers experimented with solar cells on different parts of the campus to see where they could produce the most electricity. They discovered that the best locationwas at St. Clement’sHall. The solar cells there dramatically. It would also reduce CO2 emissions by 521,702 lbs. a year and be enough to save 10,869 trees.

Boston College is exploring new ways to expand their usage of solar cells. They may be able to invest in more effective solar panels that can generate far more solar energy.

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