Combined Heat and Power

I just completed a webinar refresher on combined heat and power systems.  If you don’t know or have never heard of a combined heat and power system just picture a jet engine that doesn’t move.  The heat coming out of the exhaust is used to make steam.  On the other end, the rotating fan is connected by shaft to a generator and produces power.  Another type of system uses a boiler to make steam.  The waste heat from the flue gas is reclaimed using a heat exchanger to make additional steam.  The primary steam is then routed to a turbine which in turn, turns a generator and makes electric power.  The secondary steam is sent to whatever process will utilize the steam, such as an absorption chiller, for air conditioning.  Most CHP systems are well suited for industrial applications where large quantities of steam and power are required. However, smaller systems are also made and suited for light commercial applications.  Advertised efficiencies run between 70 and 75% depending on manufacturer.  These machines are fairly reliable and so, in the course of my practice, I have only encountered one instance where a gas turbine (jet engine) failed to perform as required.  Two engines were installed in a university setting and used to provide steam and power to various campus buildings.  Shortly after installation, it was noted that one of the gas turbines was not performing as warranted by the manufacturer.  After review of the design of the entire system, it was determined that one of the gas turbines was not performing according to its design specifications. The claim was finally resolved when the manufacturer agreed to replace the machine with a new gas turbine.

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Fires and Appliance Safety

The weather has definitely gotten colder and heating systems are being put to the test. There are different kinds of systems; electric resistance, gas-fired forced air, hot water, and steam to name a few.  Regardless of the type of system, the potential for accidental fire is part of all heating systems.   During this time of year, it not uncommon for problems to develop which, when left unattended, can result in significant damage to homes and businesses.  For example, furnaces, both gas and electric, should be cleaned at least once per year; at the beginning of the heating season.  Some people think that just because they change their air filters every once-in-awhile maintenance is complete.  NOT SO!  Depending on the efficiency of the filter in use, some dust particles will pass through the filter media and accumulate on blower blades, motors, and heat exchanger surfaces.  The burning smell often detected when the furnace is first started is the result of dust accumulation.  If the furnace is never cleaned, dust accumulation can ignite and spread outside of ductwork.  Similarly, if the controls area is never cleaned, burners can become clogged resulting in poor combustion and sometimes, delayed ignition.  Delayed ignition of gas/air mixtures can become explosive and when ignited, can release a tremendous amount of heat with deadly force.  Poor combustion can also produce carbon monoxide which when inhaled can be deadly, especially to elderly people and young children with respiratory problems.  Similarly, electric heating systems such as heat pumps should be checked for proper operation as well as components that are in good working condition.  One of the biggest problems that should be guarded against is the wiring insulation that becomes brittle with age and cracks.  Exposure of conductors can result in short circuiting leading to a fire which can then spread to the structure.  Just because a circuit is protected with a circuit breaker doesn’t mean that a fire can never develop.  Circuit breakers are current limiting devices NOT thermal limiting devices.  Heat exchange coils, motor, fans, and blowers in heat pumps should also be kept clean.  Heat pumps come in different configurations such as air to air, air to water, and air to ground.  In the last two configurations, a fluid such as water or glycol is circulated to transfer heat to or from the heat pump.  In order to do so, a pump is used to circulate the fluid and must also be serviced at certain times.  Failure to do so can result in pump motor burnouts that could result in fire.  Remember, the pump and its motor are usually two separate components unless intentionally manufactured as a single unit.  Lastly, there is not much that can be done with hot and steam boilers except to make sure that the wiring is in good condition, stack temperature is not excessive, and piping is also in good condition.  Also, remember that piping can also be a source of ignition.  Hot piping can ignite combustibles if contact is maintained long enough.  Maintenance is the key to preventing fires in heating equipment.

Climate Change and Renewable Energy

The conference on global climate change taking place in Paris is something that all people should be watching.  We are all aware of the drastic weather changes that have been occurring in recent years.  We are also aware of the fact that if we as a people don’t cut back on emissions of carbon dioxide, the climate change problems will only get worse.  So, where’s all the carbon dioxide coming from?  One of the industry’s responsible is the power industry.  Unless a plant is nuclear powered, it takes the combustion of a fossil fuel to make steam.  The steam is then used to turn a turbine which in turn drives a generator.  Technology currently exists where electricity can be produced directly or steam made and electricity produced indirectly.  Two of those technologies involve solar and wind energy.  Much has been written about solar and wind energy, particularly the cost.  The Tennessee Valley Authority (TVA) advocates that the use of both solar and wind energies and has created programs such as the “Green Power Providers” and the “Solar Solutions Initiative” to promote renewable energy solutions.  If we are going to do our part in saving our planet, what we need is more investment in renewable energy specifically solar and wind energy.

 

 

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