LPG: OVERVIEW and FACTS
Why propane? As we all know, it's difficult to store large amount of gasoline for a long time because it evaporates under normal conditions. About a century ago, scientists discovered that several gases could be changed into liquids and stored in bottles. The most abundant of those gases was propane. Nowadays, it is sold as liquefied petroleum gas (also referred to as LP-gas or LPG), and is widely used for heating homes and for operating various equipment.
Technically speaking, propane is a hydrocarbon C3H8. It is a colorless gas, which for practical use is produced as a by-product of both natural gas processing and crude oil refining. Commercial LPG normally also contains butane, propylene (5% maximum) and an odorant. It is a popular choice of fuel because of its very low boiling point of -42 °C. LPG vaporizes once it is released from a pressurized container, so no carburetor or other vaporizing device is required. LPG can be stored as a compressed liquid in steel containers with the sizes ranging from small 5 lbs BBQ cylinders to huge 4500 lbs stationary tanks. Large tanks can be installed above ground near the house, as well as underground. When you buy a new container be sure it is purged to ensure that there are no water and gas contaminants present.
PROS AND CONS OF PROPANE GENSETS
A propane generator is actually a set that contains an LPG-fueled engine and an electric generator head. LPG gensets range from small portables to large standby systems. Depending on the size, they can power small appliances and tools or an entire home. They can also be used in private off-grid homes as a prime power source. LPG price generally follows crude oil price trends. However it has a lower BTU content and slightly lower efficiency than diesel and gasoline. With the same HP of an engine, a LPG powered model will generate about 15% less power than a gasoline model, and 30% less than a diesel. Although LPG is normally cheaper than gasoline or diesel, its lower cost per gallon may not completely offset its lower efficiency, which makes it a bit more expensive fuel choice. However, if you plan to use the propane genset only in an emergency, this does not present a real issue. You can find more details in our guide to selection and buying a standby generator for the home.
LPG standby gensets for whole house are most commonly used in residential areas not serviced by the natural gas distribution system. Many consumer-grade stationary LP models can also run on natural gas, so their part numbers are sometimes the same. The pipe sizing, construction and layout are specified in NFPA 58 as well as state and local codes.
As for portable gensets, selection of the fuel depends on your application and cost considerations. If you have to frequently move your equipment from place to place, such as on construction sites, dragging a propane cylinder along with the generator may be inconvenient. For such applications diesel models with built-in on-board fuel tanks make more sense. Of course, gasoline devices have the tank too, but I would not recommend them because of their lower reliability. For an emergency home use, in my view an LPG-fueled portable is a better choice because propane can be stored practically forever and it will not gum up the engine's fuel system. An important advantage of propane is it's the only type of a transportable fuel that can be refilled during a major blackout when gas pumps may not work. And if you already have a large propane storage tank for heating and cooking, you can use it to hook up your LPG portable device for a long runtime. You just need to install an additional pressure regulator.
If you want to estimate how long will it run, see the product spec -- it usually states the fuel consumption. For example, Generac's 17 kW model 5873-1 consumes 2.57 gal/hr at full load. This means a 500-gal tank would last for 194 hours or 8 days if you don't use it for anything else. A propane genset may also be a good choice to supplement a solar powered generator in off-grid homes. By reliability and price, LPG models are placed somewhere in the middle between diesel and gasoline models. Generally, portable propane gensets are cheaper than diesel-fueled devices, but cost some 20 to 50% more than gasoline ones. Typically, their engine may last longer than gasoline fired one and will start better in cold weather.
From the environmental standpoint, propane produces less carbon emissions and is more environmentally friendly than other fossil-based fuels. It is considered safer to use- a properly functioning LPG appliance produces less carbon monoxide or other toxic fumes. However, its fumes are flammable and potentially explosive. Since some carbon monoxide still produced during so-called incomplete combustion of propane, propane generators should never be used indoors-- just like all other types of gensets they have to installed outdoors only.
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