First lets determine your power and living requirements;

Determine which appliance you want to keep operational during a power outage. Personally I would want to keep the lights, refrigerator, telephone accessories, heater fans (using gas, propane or oil fired heaters), television, stereo, computer, garage door opener, microwave, hair dryers, and electric blankets operational. Also any medical equipment and/or water pumps. I would make a list of all the appliances and their load ratings in either watts or amps and make note of voltage (keep everything consistent). This list would provide an idea of how large of a generator or inverter I would require. I would make some assumptions that not all the lights will be turned on at the same time in order to reduce my generator size. I would assume that all appliances, which are automatically cycled, could come on at the same time, example refrigerator, heater fans, and water pump.

The all-electric homes pose special consideration due to the very heavy power demands from the all electric: water heater, oven/range, space heaters or HVAC, and clothes dryer. And it is typical that all these devices could operate at the same time.

Next I would make a list of appliances of lower priority, here is where I could wait for available power in order to use them, examples include the shop saw, air-conditioner, electric spa heater, vacuum cleaner, and etc.

Some things to consider for managing the all electric home:

Use a heat exchanger on the exhaust of the generator (AC or DC) and recycle this energy for heating the hot water. You can easily get 5 kW/hr (17,000 BTUs) of waste heat from the exhaust in generating 6 kW/hr of electricity. If you recycle the heat from the engine’s radiator you will be able to capture another 17,000 BTUs (total of 34,000 BTUs of heat). The reclaimed heat may be sufficient to heat both the home and hot water.

If there is sufficient interest Polar can provide heat exchanger kits for the AC generators.

If the electrical load on the AC generator drops so will the amount of heat from the exhaust and radiator, therefore a small electric heater may still be required to load the generator.

The DC generator can be fitted with a heat pump, the heat pump while providing heat or air conditioning loads the engine providing more available heat from the exhaust and radiator.

A heat exchanger can be fitted to the clothes dryer so this appliance can also operate off the waste heat from the generator.

The electric oven and range could be converted to propane if gas service is not available. It can operate from the same propane tank that fuels the generator set. In my opinion gas does cook better than electricity. Many people are planning to use wood stoves (make sure they are legal in your area).

Using electricity to produce heat has never been as efficient as using fuel (natural gas, propane, or fuel oil).

Installation considerations (more on this subject to follow at a later date):

Fuels must not be located inside the home, basement, or garage.

A sound attenuated enclosure adds considerable cost to the generator set. Operating the generator in the garage or basement increases the risk of fire or carbon monoxide poisoning in the event of a fuel or exhaust leak. The exhaust must be directed so the wind does not blow the gases into your or your neighbors’ home.

The minimum noise specification for an enclosed generator set (AC or DC) should be 65 to 68 dBA at 7 meters. Above 70 dBA the generator is unpleasant and stressful to you and your neighbors.

With either the inverter system or AC generator a transfer switch is required to disconnect the house from the utility grid. If you do not disconnect, your small power source will then be connected to all the other homes (overload!) or if the powers comes back on your AC generator can be damaged (some inverters are protected). More on this subject later.

You must investigate the building and local community codes for the permitting process and regulations. Generally the smaller generators have less restrictions.

Operational considerations using an AC generator:

To effectively keep your space heater and/or refrigerator operational throughout out the night or day the (AC) generator will have to operate continuously. The increased run time creates significant engine maintenance. Most homeowners are unable to provide this level of mechanical maintenance and therefore the generator become less reliable and prone to quit when it’s needed.

Operating a generator with a small electrical load is not fuel-efficient. With AC generators it will not be practical to start and stop the engine every time an appliance needs to cycle on. This is better suited for an inverter.

Engine and Alternator life

The more hours the generator runs the shorter its life span and more it costs to generate the electricity.

Most all engines used for these small (less than 20 kW) generators have a design life of about 1,000 to 2,000 hours burning gasoline. You can overhaul the engine a few times to extend the life to between 3,000 to 5,000 hours. Propane and natural gas fuels greatly extend engine life providing that the conversion is done right and the engine is de-rated to allow for the higher combustion temperatures of propane and natural gas. In my opinion, there is little data on the operational life of smaller engines using gas as a fuel. Diesel engines will have a longer design life typically in the 5,000-hour range and with over-hauls lasts around 15,000 hours.

Some manufactures such as Lister Petter have converted diesel engines over to spark ignited gas engines. These engines are very heavy duty and offer life spans in the 40,000-hour range. These engines are expensive to purchase but the cost of operation is lower.

Most AC alternators have an average life span of 3,000 to 5,000 hours before requiring a re-build. The most common failure problems occur in the rotor. The centrifugal forces and vibration tend to pull apart the wires and other components located in the rotor.

A well designed DC generator using a solid rotor designs should last a very long time (20,000 to 40,000 hours). The limiting factors are abrasive particles in the air blown against the stator windings eventually wearing down the insulation, high temperature ambient causing the insulation to degrade, or a catastrophic engine failure causing the rotor to be slammed against the stator.

Fuel Selection:

If my home were serviced with propane I would use a propane-fueled generator with gasoline as a backup fuel. My house does have natural gas service so this would be my primary fuel and I would probably use propane as a secondary fuel (I use propane for my barbecue). In California, if there was an earthquake the natural gas lines are automatically shut off, also a fire, flood, or landslide can shut off gas service. Still another concern is if the Y2K event did shut down power and if a large number of individuals used natural gas, then the existing pipe lines may not be able handle the increased demand. A second fuel source is recommended. The second source would be either propane or gasoline. Propane would be cleaner burning and reduces engine maintenance, but during an electrical shortage there may shortages in propane service. I guess the solution would be having the capability of burning all three fuels. Burning multiple fuels adds to the cost of the generator.

Polar can provide engines to burn: natural gas, propane, diesel, kerosene, alcohol, fuel oil, but not all at the same time or in all combinations.

Energy efficiency in a very important factor in system selection not only to reduce operational cost but also to reduce the amount of fuel stored on site and the number of refueling trips.

AC verses DC Generator System

The lowest cost technology to purchase is the AC generator readily available from Honda, Onan, Kohler, Generac, etc. Presently it costs more money to manufacture a DC generator than an AC (due to the cost of magnets) and adding a battery and inverter further increases the cost. However, if the generator is to see significant use then the DC generator system may offer an overall cost advantage.

The concern over using an AC generator is being able to maintain proper engine speed. If the engine develops a simple mechanical (carburetor) or electro-mechanical (spark plug, governor) problem the engine speed will change and cause the electrical power (frequency and voltage) to become unsuitable causing damage to certain appliances. The majority of small generators are used for temporary applications and typically power lights, power tools, and other devices that can tolerate a wide swing in voltage and frequency. The concern is the unattended operation (i.e. at night) of the refrigerators, fan motors, and any electronics left on such as computers, televisions, and stereos, etc. If there is a problem, it’s important to shut down the generator as soon as possible. The are automatic devices which monitor the generator voltage and frequency and will disconnect the generator set via the transfer switch should a problem arise. These protection features are important, but the end result is that if the problem arises you are without power until the mechanic gets there.

The DC generator system consists of: Battery, inverter, transfer switch, and DC generator. Some inverters have the transfer switches built in. The battery stores the energy then supplies it to the inverter to convert from DC power to AC power. The DC generator charges the battery to replenish the energy. The system has the following advantages:

An inverter can silently deliver power day or night. Storing (DC) energy in a battery, then having the inverter power the AC appliances as they are required or cycle on solves the problem of having to run and AC generator 24 hours a day. It makes no sense to run a generator overnight so that the heater fan and controls can operate, refrigerator can cycle, and your VCR can record a late night movie (the light electrical load wastes fuel and increases engine maintenance). A good inverter/battery is more reliable than any engine and can provide AC power in an instant.

A battery can store the electrical energy produced by a DC generator directly. If the engine develops a problem causing a change in its speed there is no effect on the battery, nor the inverter and appliances. Speed regulation in a DC generator is not very important and this reduces your maintenance and repair.

Micro cogeneration:

Whether you chose the AC generator or DC generator and inverter based system the Y2K event will be expensive to prepare for. However, if the generator could generate power at a cost lower than the utility company, and/or if the utility company provided incentives for customers to generate their own power during peak demand periods then the installation of a power system is more economically justified.

A micro cogeneration unit can consist of:

Engine converts fuel to mechanical energy.

Alternator, converts mechanical energy into DC electricity.

Heat exchanger, to recover heat from the engine’s exhaust.

Heat exchanger, to recover heat from the engine’s radiator.

Belt-driven refrigeration compressor, to provide air-conditioning and heating (heat pump).

Heat pump heat exchangers, to provide space heating and air conditioning.

Auxiliary heat exchangers, for hot water, heating swimming pools and spas, etc.

Polar has build (and is under test) micro-cogeneration units which consists of: a generator which produces DC power and makes use of the engine’s waste heat for heating and hot water. Coupled directly to the engine is a heat pump to provide air-conditioning and/or additional heat for hot water and space heating. With an engine driven heat pump one Btu of fuel can generate a total of 1.3 to 2 Btu’s of heat depending on climate.

Using the AC generator to power a heat pump or air conditioner:

It is not energy efficient to use an AC generator to power an electric air-conditioner. Consider the overall system:

The fuel is converted into mechanical energy via the engine at a 70 to 80% loss in energy (20 to 30% efficiency).

The mechanical energy is converted into electrical energy at a 20 to 40% loss (contrary to advertising most AC generator efficiencies are 80 to 60%).

The electrical energy is now reconverted to mechanical energy using the refrigeration compressor motor at a loss of 30 to 40% (the sealed PSC motors are only 60 to 75% efficient and the three phase motors are 70 to 80% efficient).

If we eliminated the generator and motor’s energy losses we could save considerable fuel and be able to use smaller engines.

Here is the math:

With a direct drive air-conditioner using a 25% efficient engine:

1. 75% of the fuel energy becomes heat and 25% is converted to mechanical energy for direct drive refrigeration.
2. To produce 12,000 BTU of air conditioning for one hour will consume 0.473 lbs. of propane.

With the most efficient AC generator, engine, and electric air-conditioner:

1. 75% of the fuel energy becomes heat and 25% is converted to mechanical energy.
2. Of the 25% mechanical energy only 20% gets converted into electricity using an 80% efficient generator.
3. With 20% of the electrical energy only 16% gets converted back to mechanical energy using an efficient 80% compressor motor (three phase).
4. To produce 12,000 BTU of air conditioning for one hour will consume 0.738 lbs. of propane, this is 1.56 time more fuel than the direct drive system. Over a week in the summer this amounts to a very considerable fuel difference.

The efficiencies of a DC generator/inverter system verses an AC generator are:

The conversion of DC power into AC represents an extra power conversion step. However the efficiency of a good inverter (90 to 94%) and DC generator (80 to 85%) should equal the efficiency of a good AC generator (70 to 80%). Some may argue that there are more efficient AC generators available but the DC generator still comes out ahead in that the speed can change to match the load saving fuel. Most AC generators can not take advantage of variable speed to improve fuel efficiency. Others can argue that there are variable speed AC generators available, but most of these products are DC generators with an inverter built in.

The efficiency loss in a DC generator and inverter system is in the battery charge/discharge cycle. A battery is only 80% to 40% efficient depending on the age of the battery and charge cycle method. I have heard arguments from engineers claiming that batteries are 90 to 100% efficient and their reasoning is that you can put in 100 amp hours in charge and get out 100 amp hours to operate a load (discharge). The problem with this argument is that you have to charge the battery at a higher voltage than it discharges at. For example a 12-volt battery charges for one hour at 14.4 volts and discharges at 12.2 volts, we multiply the difference of 2.2 volts times the 100 amps to find a loss of 220 watt hr. In addition, we all know that as a battery ages it takes more energy (volts X amps X time) to recharge the battery.

To maximize system efficiency we need to minimize the depth of the charge/discharge cycle of the battery. Let the generator cycle on to power the long run and heavy power loads and let the generator stay off when powering the short duration loads such a 5 minute microwave operation or light electrical loads such as a small stereo set.

What type of battery to use:

My first choice is to use the same type of battery that is used in electric forklift trucks. These batteries are proven to last a long time under daily cycling. Just ask one of the operators at one of the warehouse stores. These batteries were designed to cycle once a day or every other day. Not cycling these batteries actually shortens their life.

There is an attraction to use the sealed lead acid batteries because they do not require the maintenance of having to add water. I do not recommend these batteries because of their expense and they are prone to failure in warm climates. These batteries are better suited for use as standby batteries in UPS operations inside air-conditioned offices.

Installation of batteries is very critical due to the possibility of leaking acid and that during the charge cycles the battery releases hydrogen and oxygen gases. This is true for all chargeable batteries including starved electrolyte and valve regulated (sealed type) batteries. I recommend a separate and well-ventilated enclosure next to the generator. The important factors for enclosure design is to: restrict access to children (lockable), have a plastic bottom for a containment of spills, keep the solar radiation from building up heat inside, allow the batteries to cool during charging, and provide convenient access for adding water to the cells. Polar does manufacture battery boxes.

Eventually I see the use of the new high performance batteries presently being developed for electric car applications replacing the forklift type batteries. I also foresee these DC generator systems being use to recharge the electric car batteries and at the same time cogenerating heating and air conditioning.

Solar and Wind Power:

Solar photovoltaic (PV) arrays produce DC power; wind generators can produce AC or DC power. The DC generator with inverter and battery provides a system that allows simple integration of wind, solar, and hydroelectric technologies.

For the past 20 years the photovoltaic industry (and Department of Energy) has been predicting (or promising) low cost photovoltaic product. 20 years ago the cost was about $15.00 per peak watt (ppw) with the stated goal of $.75 ppw. Current costs are in the $5.00 to $6.00 ppw, retail. I foresee the cost dropping to around the $3.00 ppw in the next 2 to 4 years and I doubt that the cost will ever come close to $.75 ppw.

Wind generators are only practical for farms and homes on large open areas. They produce noise, requires open space, and their high towers are often unsightly.

If my house were not connected to the utility grid, I would install a 500 to 1,000 pw PV array in addition to a DC generator. The DC generator would provide the bulk charge to the batteries early in the morning. The PV array would provide the finishing charge in the afternoon. The arrangement will save fuel and engine maintenance. The PV array also to keeps the batteries charged when on vacation so the generator would not have to run. As the cost of PV became cheaper, I would add additional PV modules to the house and become less dependent on fuel.

What about fuel cells and other technologies?

Fuel cells is a technology which produces DC power by combining two or more chemicals together through a catalyst. Hydrogen and oxygen are the two most promising (and popular) chemicals. What keeps the technology from being commercialized now is the process of generating the hydrogen from the hydrocarbon fuels such as natural gas and propane. Due to the complexity of the fuel conversion process there will be a minimum practical size for economic commercialization. This minimum size maybe 10, 20 or 100 kW. If hydrogen could be delivered to the users then the on site fuel conversion process would unnecessary. The fuel cell would then be very simple in construction and without minimum size restriction. Hydrogen is the cleanest burning of all fuel but there are many individuals who fear hydrogen as a fuel and oppose its application. There are technologies available to store and transport hydrogen but the other fear is product liability. With out present legal system it even would be impossible to introduce gasoline as a new fuel.

Personally I feel that fuel cell technology is 10 to 15 years off into the future. The important point to note is that the fuel cell produces DC power, so an investment into a DC generator system would mean that if fuel cells for the home are commercialized then only the DC generator get replaced after it wears out. The inverters, batteries, and even the heating system remains in place. The fuel cell will also produces waste heat that can be used for heating.

Turbo alternators are practical in sizes of 20 kW and larger. The problem with turbines under 20 kW is poor efficiency due to inability to improve upon the turbine blade clearances as the unit is reduced in size. Turbines are not very practical using low pressure natural gas, the cost of equipment to compress the gas so the it can be injected into combustion chamber is expensive and can consume up to 10% of the electrical power. The equipment required compressing the natural gas off set any advantage of size, noise, reliability, and efficiency that a turbine might have to offer. It takes much less energy and equipment to pressurize and inject a liquid that gas, therefore liquid propane, alcohol, and diesel are good turbine fuels.

Turbines are better at producing DC power than AC. To produce AC requires a high-speed gearbox that adds to cost, maintenance and lowers efficiency.

So far turbines are too expensive to own and operate.

Sterling engines are too expensive and complex to maintain.

Other than the technologies discussed herein I see not other near term technologies as power solutions.

Where does Polar Power stand?

Polar has 20 years experience (since 1979) in designing and building DC generators, inverters, and renewable energy systems.

We have manufactured micro-cogeneration (air-conditioning, heating, and electrical power generation) systems in small quantities over the past 4 years. We have almost no data on their financial impact. Once the systems get installed we have had no means to collect data. Personally, I have no interest in calculated projections because of all the use variables and other factors such as the regional variations in fuel quality and cost verses the local utility costs. The use factors are considerable from region to region. For example, I live near the ocean in Southern California, I have very little need for heat and air-conditioning, and this is in high contrast to the needs of homes in the local desert for heating and air conditioning, or the mountains for heating only.

There has been strong interest from the utility companies on these products. Polar will be providing a micro-cogeneration system in the next few weeks to a utility company for testing and financial analysis. It will be in a desert environment and I can keep you posed as the information is received. Additional utility companies have contacted us for product to test and evaluate.

What next:

Before purchasing a system I would contact the renewable energy department of my local utility company. If there is no energy department try the sales office. My intention would be to get financial and technical assistance. Be prepared for the run around. The goal is to find out if the utility company will:

1. Purchase the equipment for you then lease it to you over a 5 to 15 year period.
2. Give you cash back incentives or discounts on your utility bill.
3. Buy and install the equipment for you and use your home as study site.
4. Discount your utility bill for generating your own power during their peak demand.

If you are able to reach an individual with intelligence and interest, their first concern will be the effect our your equipment on their power grid. Utilities are generally not interested in buying back electrical energy because they fear the quality of power and the effect your equipment (or maintenance of the equipment) would have on the grid if something should go wrong. The utility appears more supportive if you tell them you have no interest in being connected to the grid while your are generating your own power (at least for now).

The next organization I would contact is the state government’s energy office, renewable energy office and discusses your project and any response you might have received from the utility company.

I would also try to gain help and support from friends and neighbors. After all I would not want to be the only one on the block with electrical power.

I am sure that most people you contact at the utility company and State Energy office will tell you that there will be no problem with power availability during the Y2K event and they may be right. No utility companies or state agency will want to participate in a program based on their potential failure to handle the Y2K event. Your point of focus should be on backing up your utility power for any natural event (i.e. storm, earthquake, etc.) and cogeneration of your own energy needs using clean burning gas.

What does Utility Deregulation have to do with the subject above?

Many individuals believe that quality of power service will degrade with deregulation.

Many in the utility industry are concerned about competition within their "captive" markets from groups that can generate their own power at a rate lower than what they can purchase. The utilities position could be to join in and help finance, install, and maintain the equipment for the users and user groups.