QUESTION: I would feel more comfortable with some emergency electricity for my home, but I cannot afford a big generator. What type of simple, portable battery power supplies are available to power some essential items?ANSWER: With today's homes and families totally dependent upon electricity for even the basic necessities, it is wise to plan for power outages. Whole-house generators are the best option, but they cost many thousands of dollars to install and require gas or diesel for power.Portable power supplies, or even your automobile battery, can provide electric power for a television, radio, lights, and some other essential items.The problem is most batteries produce 12-volt direct current electricity, but most items require 110-volt alternating current.There are devices called inverters that convert 12-volt battery power to 110-volt house power. There are small 100-watt units that plug into the lighter socket in your car. The wattage rating tells you how powerful a device can be plugged into the inverter.This could be used to operate a small television, recharge a cell phone, run a small pump, etc.More powerful, 750-watt inverters are also available. These have jumper-type cables that are attached to a battery. They are small, about 9-by-5-by-3 inches and have two 110-volt outlets. As long as the battery is charged, these will produce usable electric power.Another source of power is an uninterrupted power supply (UPS) for a computer. These have a battery and a built-in inverter. It is wise to always use one to protect your computer and it will double as emergency power.There are also special portable power supplies available. These are generally designed for use during emergencies, but they also function well as portable power when you are camping or working outdoors. Most of them include a set of jumper cables to start your car if the car battery goes dead. Many also have built-in tire pumps, emergency lights and efficient (LED or fluorescent) work lights.The amount of 110-volt electric power they produce depends upon the size of the internal battery and the inverter. A 10- to 20-amp-hour battery is typical and it indicates how much electricity is stored in the unit.Its wattage rating indicates the maximum electricity output of the inverter. If you plug in items that draw too much current, the inverter will overheat and shut off.You can always store extra batteries for more power and keep them charged with solar cell trickle chargers.Also consider getting an additional lower-powered unit, such as a Storm Station, with one 110-volt outlet and a built-in light, radio and television sound. These are lightweight and easy to handle.The following companies offer portable power supplies: Black & Decker, 800-544-6986, www.blackanddecker.com; Clore Automotive, 800-328-2921, www.jumpstarter.com; National Solar Tech., 800-310-7413, www.nationalsolaronline.com; Vector Manufacturing, 866-584-5504, www.vectormfg.com; and Xantrex, 800-670-0707, www.xantrex.com.Send inquiries to James Dulley, Butler Eagle, 6906 Royalgreen Drive, Cincinnati, Ohio 45244 or visit www.dulley.com.

QUESTION: I have heard of solar curtains that are hung inside the window. They are supposed to absorb the sun's heat during the day and give it off at night. Can lightweight curtains really store much heat energy?ANSWER: The concept of using solar curtains is attractive, but lightweight curtains cannot store much heat. It takes a lot of thermal mass to store heat.Phase change materials would work better, but they would still be pretty heavy.Thick standard curtains will not store heat, but they will reduce the heat loss through windows at night. They should cover the entire window opening and fit as snugly as possible against the wall.James Dulley has a degree in mechanical engineering. His Sensible Home column appears in 400 newspapers.