Modern living is postulated on grid connection. Communications, food safety, preservation and preparation, and the ability to keep warm in winter are quickly compromised without power from the electricity grid. Even more important to many are their battery-powered toys, whose powered on is a prerequisite for a life worth living.
Loss of juice in our segment of the grid is a problem to be solved by each of us. And it should be addressed now, as it will be too late at the point of future failure. We need to characterize the problem, look for examples of solutions that work, and calculate the best solution whose cost matches our expected benefit.
The grid is normally reliable; thank you government and utility business. For most of us suburbanites, living near a substation and having weather on the milder side, a couple of two-hour outages and perhaps an extended eight hour outage may be a typical year’s experience. For such inconvenience, no backup is really required. We either grin and bear it, or gut it out, depending on our personality type.
But there are future scenarios with more dire effects to be sure. Continued population growth and increasing energy use per capita will increase strain on an already strained grid. Lack of growth to meet future demand, coupled with more severe weather patterns due to global climate change, will combine to increase brownouts and blackouts. Adding to the problems inherent with the grid itself, there is increasing threat of cyber-terrorism and physical terrorism directed toward the grid. Utilities and government now conduct ‘fire drills’ across the grid to test for soft spots and to plan for detection and combat of terrorism threats.
Growth in the system is constrained by the capital-intensive nature of new generation capability, by the few carbon-light choices available for such new generating capacity, and by increasing hassles of environmental/social impacts due to routing new transmission lines. New line routes encounter a variety of pitfalls, from interfering with wildlife leks, to annoying the politically-connected whose ranchettes might lie in the potential right of way.
Beyond man-made problems, there is consideration of natural disasters that will impact the grid, from earthquakes and vulcanism to great storms. It is a complicated future that the average person will be hard pressed to plan for with competence. Yet as with any form of insurance, responsible people in a position of caring for loved ones will likely invest some thought and preparation. Our answers will vary, with the largest variance due to income level.
For those in the upper 5% of income distribution, full-up redundancy in backup power generation can be a simple choice. But for the other 95% of us, an investment in power insurance should be tailored to the actual probability of electrical outages of a given severity, which can vary considerably in normal experience, and is subject to the indifferent influence of once in century and once in millennia events.
Showing Us The Way
Some of our agrarian societies have chosen to live off the electric grid. With proper dwelling design and sources of other energy such as water, coal, kerosene, wind, or wood, such life choices are easily accommodated within a life style that harkens to a 19th century rural existence.
Modern green eco-experimenters, many with a taste for remote living, also choose to live off the electric grid while still holding to their modern sensibilities. They do so with the aid of a modern invention, the photo-voltaic (PV) cell. Their efforts are making solar power an increasingly reliable and cost-effective solution. Here viable cost effectiveness is based on an investment amortized over continuous 24/7 energy usage.
Apart from the 19th century agrarians and the 21st century solar explorers, most American residential dwellings of the last century are designed for connection to the electrical grid. For dwellings so designed, disconnection is a problem that is costly to overcome completely, with fully automated backup facility costing a similar amount to an inexpensive car. Not many people would invest in a car if they planned to drive it only once or twice a year. So for most, a compromise solution is needed.
Solution scalability is perhaps the most important parameter. We are planning for an eventuality where the grid will be unavailable for an unknown period, usually hours, but perhaps days, perhaps weeks. These are tough requirements. We can limit the open-ended character by saying if the outage is over a month with no end in sight, we will bug out temporarily for a vacation and come back when the emergency is over. So we consider a duration range of four minutes to four weeks.
We consider different approaches. From the agrarian fundamentalists, we consider switching temporarily to 19th century resources. This is the default solution of all who don’t recognize or address the problem of backup. It helps to have a wood supply and a wood-burning stove that supports cooking, and some lanterns with suitable fuel or supply of batteries.
The few folks already addressing our problem seem mostly to choose the most flexible and inexpensive alternative source of power, the portable, fueled, motorized alternator, aka generator. This will be our basic tool also. It provides automatic voltage regulation (AVR) to produce sine wave power similar to that available from the grid, and hence will likely run all the electrical devices in the typical home. With a generator, scaling to longer run durations is mainly a function of fuel supply and operating cycle. Operating cycle can be tailored to restricted and sequenced load usage.
From the 21st century experimentalists, we consider battery backup, with a parallel recharging source for the batteries, typically solar PV or generator. I didn’t consider whole-house battery backup in the form of Uninterruptible Power Supply (UPS), because a power inverter with sine wave output and of kW capacity matching our house loads will cost 5-10X as much as an equivalent portable generator, when considering cost of required batteries and the generator (or even more expensive solar panels) required to keep the batteries charged.
The advantage of a battery-backup UPS is that it is available 24/7, with recharging generator only running periodically when triggered by the inverter/charger. With generator alone, we will still manually turn off the generator periodically, to conserve fuel. During down times, we will be without whole house power, but can still run selected lights and small appliances from a small and much less expensive UPS.
During periods of grid power unavailability, our solution is thus a combination of mechanical, motor-driven electricity generation, together with modified daily energy usage, one or more modular UPS and/or rechargeable, battery-operated appliances to keep the essential lights on and labor-saving devices whirring while the generator is cycled off. Also on hand are a gas fireplace convertible to wood, and propane BBQ.
Propane (LPG or liquified petroleum gas) is our disaster readiness friend; gasoline, kerosene, and diesel, not so much. The latter present highly flammable storage dangers and degrade over time. And they will gum up the generator’s carburetor if left to stand there without purging after use. A generator that won’t start when needed is a major PIA. Gasoline is available from vehicle gas tanks as an alternative fuel reserve. A siphon is a useful emergency tool.
Since propane fuel is more practical and safe than gas/diesel fuel, we looked for a dual fuel or tri-fuel model, presenting limited choices in a portable generator. Propane conversions for gasoline models are available for some models, but we avoided that extra hassle by picking a model already configured for flex-fuel, including LPG.
We run the generator off 20lb propane tanks designed for the barbee. We start with two. All together, our dual fuel storage reserve should provide on the order of 40 hours of generator usage, clearly not enough for full time use for weeks on end (although propane could be supplemented with gas from the car’s gas tank). Therefore, we scout nearby propane sources that might be accessible in an emergency. Lines there should be shorter than at gas stations. 100lb propane tanks are also available, but a senior citizen such as myself might struggle hauling them in the car to a refill station and back.
Our generator is sized for our expected emergency load. Because we have no pumps to operate, and our major heating appliances are natural gas-powered, we can get by with considerably less generating power than homes having heavy loads needing emergency power. On the other hand, if we lose natural gas supply, we may need electric backup space heating.
Our two unpredictable (non-sequenced) loads are both thermostat-controlled, the heater furnace blower motor and the refrigerator compressor. We size our need so that when both these loads are active simultaneously, no more than half our emergency power is consumed. All other electrical loads are small or can be scheduled sequentially so as to not exceed the other half of our generating capacity.
Turn-key, single purpose, permanent, whole house propane generators are marketed as providing peace of mind. But they can cost over 10X more, and you can’t load them in the truck and take them with you to job site or outback. Any generator larger than the calculated minimum size wastes resources. Physical dimensions and weight, purchase cost, operating cost, and loss of portability all argue against going larger than needed for an emergency backup feature that sits idle nearly always. Thus whole house, fixed installations were not considered.
To meet the minimum of our needs, we chose a portable generator in the 4kW power range. While a slightly larger generator would have provided us with a bigger margin for error, there were no affordable flex-fuel models (our primary functional parameter) in the next larger capacity ranges. Also, at 57 kg, ours is the largest generator that a senior citizen such as myself can safely handle alone. The next larger size is considerably heavier.
There are two ways of connecting the generator to the loads. Either plug critical appliances directly into the generator via power cords, or connect the generator output directly to the house electrical wiring, termed a backfeed system. To conveniently power home furnace blower, built-in refrigerator, and microwave, backfeed is necessary.
There are two ways to connect the backfeed generator output to the house internal wiring: right way and wrong way. There are two variations of right way. The automated right way is to install a power transfer switch. Then the house can be connected either to generator or utility mains, but never to both simultaneously. A manual alternative is to place another circuit breaker, for the generator inlet circuit, in the main electrical box and then install a mechanical interlock that will not allow generator inlet and mains breakers to be on at the same time.
The wrong way is to plug the generator directly into the 240V dryer power receptacle in the laundry room, using a kludged power output cord with two male ends. Why is this wrong? If the house mains circuit breaker is not turned to OFF first, the generator power will feed back into the utility electric lines. This wastes your power generation, threatens damage to your generating equipment, and worst of all, poses a hazard to anyone who exposes themselves to bare lines down the street that they believe to be dead. While the pros take precautions against extraneous backfeed power appearing on the lines, your neighbor probably wouldn’t.
Many people will choose the wrong way because it saves several hundred dollars of hardware and electrician services. They are sure that they will always remember to turn the house mains breaker off before plugging in the generator. Their house is still to code when a generator is not connected, so it’s hard to prevent this practice, although a burned down house or electrocuted homeowner (the bare male-end prongs are live when the generator is running) makes for a good cautionary tale.
For a transfer switch, there is the option to switch on the whole house, or to switch on a subset of circuits. Since we will choose a manual electrical source transfer via circuit-breakers, we can leave all circuits in our main breaker box and manually select which ones to activate at any time. This saves the considerable cost of adding a new breaker sub-panel and moving some circuits around.
We selected the DuroMax XP4400EH, a three-wire Electric start, Hybrid (dual fuel) model that sells widely for $650. It has good user ratings, although the manufacturer is not identified and only the point of sale representative stands behind the product. This is typical of cheap Chinese imports. Their cost makes them virtually throw-away devices, and sometimes we get lucky and get a good unit that performs reliably.
This DuroMax has a surge rating of 4.4kW and a steady state rating of 3.5kW. Given most manufacturer’s advertising exaggeration together with inherent device inefficiency, one should use figures ~10% less than the manufacturers’ ratings when actually sizing the generator to the expected load.
Generators are best stored in the garage or a shed, to keep the elements away from the equipment and to reduce the range of ambient operating temperatures. The opportunity for theft further necessitates such protective measures, for a generator attracts attention to itself in a quiet neighborhood.
A social hazard of generator operation is displeased neighbors. Noise abatement will occur in a sound-deadening enclosure. A custom auxiliary muffler or tailpipe extension can further reduce noise and help in routing hot exhaust gasses out of an enclosure. The DuroMax advertises a sound factor of <69 dB @ 20 feet. Appropriate installation considerations as above can reduce this by up to 10 dB.
Inverter generators are significantly quieter and more fuel-efficient, but add a sizable up-front cost factor. There are very few propane-fueled inverter models, and in the 4000 kW power range, the one I found costs ~$1K more.
One should start-up an emergency generator every month or so to keep it in a ready state for the next emergency. Also, it should not be run for any length of time without loads attached, due to cylinder wall glazing that will occur in no-load running. Generators like a load in the 80% rated output range. Basic maintenance is similar to automotive engine maintenance. Keep the oil full and fresh, the air cleaner clean, and the spark plug clean and properly gapped.
Our generator resides in the garage with a protective cover, connected to the house wiring via a 4-wire, 30 amp, 240 volt power cord from generator to inlet electrical connection on the garage wall. If the generator can be used from the same location it is stored, it takes only a minute or two to activate the backup power system.
The main breaker in the electrical panel is switched off, along with all non-essential circuits. The lockout device is then moved to its alternate position to enable the generator inlet breaker to be turned on and the generator start-up procedure performed. Finally, needed circuits are re-enabled at the breaker box, and the house roars back to life.
Because we did not purchase an inverter generator, ours always runs at 3600RPM to cause the alternator to produce 60 cycle sine wave power. To conserve fuel and to ease wear on equipment, we choose to run the generator only periodically. The frequency and duration of run periods is selected based on keeping our food from spoiling, us from freezing, and our batteries fully charged. We plan our power usage so that during non-generating periods, we use only battery-operated lighting and equipment. Our batteries are always charging while the generator is running.
Without an automated transfer switch, the homeowner has no way to detect when external mains power is restored other than observing neighboring use of lights. We check the mains breaker before each generator run and stop operation.