July 03, 2007

Engineers Find Way To Make Ethanol, Valuable Chemicals From Waste Glycerin

With U.S. biodiesel production at an all-time high and a record number of new biodiesel plants under construction, the industry is facing an impending crisis over waste glycerin, the major byproduct of biodiesel production.
New findings from Rice University suggest a possible answer in the form of a bacterium that ferments glycerin and produces ethanol, another popular biofuel.
"We identified the metabolic processes and conditions that allow a known strain of E. coli to convert glycerin into ethanol," said chemical engineer Ramon Gonzalez. "It's also very efficient. We estimate the operational costs to be about 40 percent less that those of producing ethanol from corn."

Gonzalez said the biodiesel industry's rapid growth has created a glycerin glut. The glut has forced glycerin producers like Dow Chemical and Procter and Gamble to shutter plants, and Gonzalez said some biodiesel producers are already unable to sell glycerin and instead must pay to dispose of it.

"One pound of glycerin is produced for every 10 pounds of biodiesel," said Gonzalez, Rice's William Akers Assistant Professor in Chemical and Biomolecular Engineering. "The biodiesel business has tight margins, and until recently, glycerin was a valuable commodity, one that producers counted on selling to ensure profitability."

Researchers across the globe are racing to find ways to turn waste glycerin into profit. While some are looking at traditional chemical processing -- finding a way to catalyze reactions that break glycerin into other chemicals -- others, including Gonzalez, are focused on biological conversion. In biological conversion, researchers engineer a microorganism that can eat a specific chemical feedstock and excrete something useful. Many drugs are made this way, and the chemical processing industry is increasingly finding bioprocessing to be a "greener," and sometimes cheaper, alternative to chemical processing.

In a review article in the June issue of Current Opinion in Biotechnology, Gonzalez points out that very few microorganisms are capable of digesting glycerin in an oxygen-free environment. This oxygen-free process -- known as anaerobic fermentation -- is the most economical and widely used process for biological conversion.

"We are confident that our findings will enable the use of E. coli to anaerobically produce ethanol and other products from glycerin with higher yields and lower costs than can be obtained using common sugar-based feedstocks like glucose and xylose," Gonzalez said.

The report in Current Opinion in Biotechnology was co-authored by postdoctoral research associate Syed Shams Yazdani. Graduate students Yandi Dharmadi and Abhishek Murarka assisted with the research. Gonzalez's research is funded by the U.S. Department of Agriculture and the National Science Foundation.
Source: Rice University & Chemical Online

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July 02, 2007

Waste Heat Driven Hydraulic Engine

Waste Heat Driven Hydraulic Engine
Deluge, Inc. has developed a thermal hydraulic engine that is now ready for commercialization. The company has successfully completed long term field testing of the technology, and has obtained patents on the design in nearly 40 industrialized countries world wide.

The Natural Energy Engine™, requires no combustion, operates virtually silently, and generates no emissions. It operates by utilizing low level heat energy ~80°C suitable for many applications, from solar, geothermal, or any other heat source, including waste heat from existing processes.

The main components of the engine system are quite simple – a piston/cylinder and a heat transfer system. The cylinder contains a piston and a working fluid, and depending on the application may have a module to reposition the piston after each stroke. The heat transfer system comprises heat exchangers, a system to circulate the heat transfer fluid (typically water), and a simple circulation controller.

The key difference between a traditional combustion engine and the NE Engine is that the NE Engine relies on the transfer of heat to, and its subsequent removal from, a working fluid within the cylinder. As the working fluid is heated it expands, providing the pressure to drive the piston, and is subsequently cooled to complete the cycle.

The Company projects that engine configurations can easily be priced at 60-85% of power systems that produce equivalent output.

The NE Engine creates mechanical energy in a three step process:
Step 1: Heated water is collected – for many applications 80°C is suitable.

Step 2: The hot water enters a heat exchanger where the heat is transferred to a working fluid. The working fluid, typically liquefied CO2, has a very high coefficient of expansion, meaning that it expands and contracts significantly, based on its temperature, while remaining in a liquid state. As the working fluid is heated, it expands, pushing a piston in the engine’s cylinder.

Step 3: Cooling water – generally in the range of 100° F lower than the input water, with varying differentials depending on the application – then enters the heat exchanger causing the working fluid to contract, readying the piston for another stroke.
The back and forth movement of the piston creates mechanical energy directly from heat energy. This motion can be harnessed to operate a motor or to perform other work. Even lower temperatures and different differentials can be utilized, all of which attest to the versatility of the engine. A formula has been developed that establishes the ratio between the volume of the heat exchanger and the volume required to displace the piston for various fluids. This formula establishes design parameters for different horsepower systems.

In typical applications, due to the natural pressure of liquid CO2, the cylinder is constructed such that the CO2 working fluid is on one side of the piston and a pneumatic spring charged with nitrogen (N2) is on the other. Heating the working fluid results in increased pressure on the working fluid side of the piston. The hydraulic pressure of the working fluid must be high enough to overcome the starting torque (static friction) of the piston. When the pressure exceeds this point, the piston moves outward, compressing the pneumatic spring. After a predetermined time period, cooling water is sent through the heat exchanger. As the temperature decreases, the volume of the working fluid shrinks. The backpressure of the pneumatic spring helps push the piston back to its starting position.
Multiple piston engines have been built and operated. In two piston applications, the two pistons can be configured so that they offset each other in a single cylinder. As one piston extends, the other retracts. Between the pistons are two working chambers that allow the engine to do work, such as compressing gas, pressurizing water, or pumping hydraulic fluid through a hydraulic motor to turn a shaft. In four piston applications, heat exchanger assemblies timed to run at staggered intervals are utilized on each of the four cylinders. Valves that direct either the heated water or the cooling water to flow through the heat exchanger are timed using the four pistons. The four cylinders work in sequence continuously applying power to turn a rotating shaft for varying applications.
Sources of Efficiency and Economy
The fundamental design of the engine provides the basis for its efficiency and economy. First, the engine has an inherent efficiency because so little energy is dissipated in heat loss and noise generation. In an internal combustion engine, for example, much of the BTU energy in the gasoline is sent out the tailpipe as waste heat, but the NE Engine can actually recycle whatever heat is not used. In part, this is because the engine operates at low temperatures – the NE Engine uses heat differentials of approximately 100° Fahrenheit to produce usable power.
Additionally, the NE Engine is more efficient because so little energy is used for indirect motions. An internal combustion engine uses a significant fraction of its power to overcome friction and operate ancillary functions, such as valves, cooling circulation, and the like. Additionally, each cylinder in an internal combustion engine typically provides power only on every second or fourth stroke, while each stroke of the NE Engine is a power stroke.
Another efficiency advantage of the engine is in power transfer. Unlike an internal combustion engine, for example, there are no camshafts with their friction and power losses, no gearing, and no transmission. Of course, in applications where linear power must be converted to rotary power, traditional methods or even hydraulic converters can be used. Although the engine’s high torque typically makes gearing and transmissions unnecessary, gearing is one option to generate even more rapid – or slower – movement than the engine’s normal cycle.
The result is a highly efficient, virtually silent, direct drive engine that can easily be configured to use no traditional fuels and generate no pollution whatsoever.
In sum, the real economic advantage of the NE Engine is its lower operating cost and increased efficiency over competing gasoline, diesel or electric powered engines. Unlike conventional engines that require costly fossil fuel or electricity, the NE Engine fuel is simply low grade heat – something that can be supplied by a variety of sources including solar thermal, geothermal, ocean thermal, waste heat or small amounts of electricity or carbon-based fuels. The engine’s ability to effectively utilize low grade heat results in minimal fuel costs.
The NE Engine is inherently simple with few moving parts; therefore, is easier to manufacture and to maintain than conventional engines. Deluge’s technology creates an affordable alternative to the more technologically complex products currently available.
Product Features and Benefits
Overall features and benefits of NE Engine technology include the following:

Proven Technology:
The engine is based on recognized, proven, understandable technology of modest complexity.
Flexible Design:
The engine is designed so that it can be fabricated using existing off-the-shelf components and machined parts from existing fabrication plants, enabling access to a diverse source of parts vendors around the world, resulting in competitive pricing.
Simple Maintenance:
Training is of a mechanical nature, and does not require expensive high tech testing equipment, allowing for a broad range of skilled individuals who can be made field ready in a relatively short period of time.
Durability:
The engine has a robust design for long functional life, and easy repair and maintenance.
Independent Power:
Self-contained products can easily be configured that work well “off the grid” in remote locations.
Multiple Fuel Options:
Multiple fuel sources include solar thermal, geothermal, ocean thermal, natural gas, propane, waste heat and others, allowing for flexibility in choosing the most cost effective and available energy and backup energy source options.
Low capital cost:
The Company projects that engine configurations can easily be priced at some 60-85% of power systems that produce equivalent output.
Low operating costs:
Depending on configurations, operating costs can easily range from 25-75% of power systems that produce equivalent output, and can actually be as little as 4% (a 96% reduction in costs) – which can justify replacement due to the quick payback.
Pollution free:
The engines create no environmental waste, are inherently safe to operate, and produce no noise. They can be configured to be entirely “green” and pollution free.
Cost Efficiencies with Size:
As engines are built in larger sizes, a dramatic decrease in cost will occur when approaching the 200 horsepower range. As with many technologies, projections beyond that range will continue to reduce the cost per horsepower.
Above All.........Operating cost is claimed to be 4-15% of the conventional engines. What more you can expect from any R&D developemnt..........
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Energy Saving Tips-1

Tips in Day to Day Life
Refrigeration / Air Conditioning
  1. Select proper size AC based on room size, family members, wall & window area etc.
  2. Keep your refrigerator & freezers filled to capacity without restricting air circulation.

  3. Regularly clean the condenser parts of your refrigerator & AC both to have better efficiency without loosing energy.

  4. Frost free refrigerators have in built heating elements which are not required during summer. So use the option of power saving mode or set thermostat at low temperature to avoid frequent power on for these heating elements unnecessarily.

  5. Both AC & Fridges should have proper gaskets for sealing to avoid ingress of hot air.

  6. Keep all liquids in the refrigerator in closed container to avoid bad smell as well as to save energy due to increased vapor load on compressor.

  7. Compartmentalized refrigerators are better than single door due to limited area exposure each time, the door is openend.

  8. Put an automatic clock (RTC) based timer to switch it off during night. This also reduces the no of on & off cycles during the life of the machine resulting in less wear & tear apart from energy saving.

  9. Try to locate AC unit on the north side of house to avoid direct sunlight.

  10. Use sun screens on window glasses to avoid radiation heat.

  11. AC thermostat setting should be ~24°C which is reasonably good & comfortable temperature everywhere.

  12. Use low wattage lighting in the rooms to avoid unnecessary load on AC.

  13. Do not use heating devies in AC room e.g. Iron, Dust Blower etc.

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Thermodynamics of Thermal Cycles

Thermal Machines

A machine is a mechanical device with moving parts that helps to do some useful action, usually work. Machines may be just mechanical (pulley-and-belt), hydraulic (water wheel, the earliest engine), pneumatic (windmill), electrical (electric motor, the most common nowadays), chemical (fuel cell), or thermal.

I am restricting it to devices that converts heat to work (heat engine), and to devices that pump low-temperature energy to high-temperature energy (by using some source of exergy), all working cyclically. The heat-pumping machine may be intended to produce cold (refrigerator), or to produce heat (heat pump), or both at the same time (refrigerator with heat recovery, or heat pump).

Heat Engines

Defining it?
A heat engine is a machine that produces work from heat, like the steam engine. Heat engines provide nearly 90% of the motive power generated in the world, the other 10% provided by hydroelectric power stations. Nearly 60% of all the world energy consumption is devoted to run heat engines, the rest being devoted to industrial and domestic heating.

A heat engine is a device where a working fluid performs four basic processes: heat input, hot expansion, heat rejection, and cold compression. By means of these internal processes, the heat engine gets heat from a hot source, produces some work, and rejects the rest of the energy balance as heat to a colder heat reservoir. All heat engines rely on the compressibility of the working fluid (i.e. a gas or vapor) and the fact that a hot expansion delivers more work than that needed for a cold compression (of a gas, vapor or liquid).

What it is for?
Motive power (engines and motors) is used as stand-alone plants to deliver motion or electricity to other systems, or within vehicles to provide motive power (propulsion) and auxiliary energy (there are nearly a billion, vehicles worldwide, more than 80% of them passenger cars). The steam engine is now only found in the largest power stations, and today the most common heat engine is the internal combustion reciprocating engine (for cars, trucks, ships, small airplanes, and stationary engines), with a third type, the gas turbine engine gaining ground (for most aircraft, the faster types of ship, modern power stations and combined power-and-heat stations).

The largest thermal power plants are vapor turbines, typically limited to 1000 MW per unit in nuclear power stations because of heat transfer limitations from the reactor (fuel-fired power stations are limited to some 400 MW per unit because of combustion intensity limitations). Gas turbines may also reach some 300 MW per unit, and the largest reciprocating engines are marine diesel engines of some 50 MW.

Thermal aspects of heat engines

Carnot cycle
With his 1824 masterpiece Nicolas Leonard Sadi Carnot was the first to provide a thermodynamic model of a heat engine, abstracting from the only available heat engine, the steam engine, to pinpoint the fundamentals: the idea of a generic working fluid, performing a generic cyclic process, interacting with generic heat reservoirs.

In his only publication, Carnot concluded that all heat engines where limited in their energy-conversion efficiency by the operating temperatures, and that the maximum efficiency is obtained when the working fluid is assumed to follow four ideal processes.









  1. An isentropic compression (D to A), to change temperature without heat transfer.

  2. An isothermal heat input (A to B), from the hot source, at the hot-source temperature.

  3. An isentropic expansion (B to C), to change temperature without heat transfer.

  4. An isothermal heat rejection to the cold source (usually the environment), at the cold-source temperature. (C to D).
Carnot reached those conclusions by a set of rational deductions, namely:

  • 'Any engine with friction would have less efficiency than one without',

  • ‘Among all engines exchanging heat at different temperatures, the one with highest efficiency only exchanges heat at the two extreme temperatures (the hottest and the coldest)' and,
  • 'All reversible engines working with the same couple of temperature extremes have the same efficiency'.

Reality
However, none of the process is 100% efficient & therefore, Carnot cycle is totally a theoretical one. The efficiency of each thermodynamic step varies & depends on the type of process e.g. step 1 of assumed isentropic compression is having a maximum efficiency of ~80%, Heat input using internal combustion have a maximum of 60% efficiency, Isentropic expansion with maximum 85% and last step may have different figures from 85 to 100% depending on direct or indirect rejection of heat. So mathematically we get 41% in overall which is quite practically achieved efficiency for IC engines and 35% for other cycles where last step is also contributing like in heat pumps etc.

This was the basis for all building blocks for different cycles generated later on in an effort to increase the efficiency of total cycle.

In Practical situations where we can have combustion temperatures limited to ~1200°C and ambient sink of 30°C, the carnot efficiency is only 80%. With a factor of 41% efficiency as explained above practically possible maximum efficiency in carnot is ~32%.


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For this series, I am dividing different cycles in the following categories, which I shall discuss later one by one.

Gas Cycles without phase change

  • Carnot Cycle
  • Brayton Cycle
  • Ericsson Cycle
  • Stirling Cycle
  • Stoddard Cycle

Gas Cycles with phase change

  • Rankine
  • Kalina
  • Regenerative

IC Cycles

  • Diesel
  • Otto
  • Atkinson
  • Bourke
  • Lenoir
  • Miller
  • One stroke
  • Two Stroke
  • Wankel

Mixed Cycles

  • Combined
  • Crower
  • Dual

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