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A Very Simple Explanation of a Backup Emergency Power System

 Copyright © July 5, 2024 by Robert Wayne Atkins, P.E.
All Rights Reserved.

Introduction

Paper Money Many people worldwide are gradually becoming aware of the possibility that some of the things that they take for granted today may not be available in the future. For example, a major war, or a major solar flare, or a collapse of the worldwide financial system, could seriously impact the way that many families live on a day-by-day basis. Therefore many families are now adding some emergency food into their pantries so that their families can continue to eat if there is a disruption in the delivery of food to their local grocery stores. These people are no longer being called "hoarders" or "doomers." Instead they are being portrayed as practical and intelligent people.

Some of these people are also becoming interested in learning a little more about how they could provide some emergency electricity for their homes. These people already know that they can use candles or battery-operated flashlights for lighting. But they also know that sooner or later their candles and batteries will be used up. Therefore they are becoming curious about some of the other options that are available for providing backup emergency power for their families.

Some of these people are investing in a generator that uses gasoline or diesel or propane to provide electrical power. This may be a good option for some people. However, eventually the gasoline or diesel or propane will be used up and then the generator will stop producing electricity.

Four other options for providing electricity are:
  1. Wind Turbine: It uses rotating fan blades to convert incoming wind power into electricity.
  2. Water Turbine: It uses falling water (such as a waterfall or a dam) to convert the continuous falling motion of water into electricity.
  3. Solar Panel: It converts the sun's rays into electricity.
  4. Geothermal Power: It converts heat energy inside the earth into electricity. (In Greek "geo" means earth and "thermal" means heat.)
This article will briefly discuss solar panels.

Discussion

The Sun A solar power system has four basic components:
  1. Sun: An energy source.
  2. Solar Panel: A device that converts the sun's rays into DC (direct current) electricity.
  3. Battery: A storage device for DC electricity.
  4. Inverter: A device that converts battery power (DC electricity) into house power (AC electricity).
Since this article is about providing backup electrical power for use by a family, this article will use a family's consumption of food to explain how a solar power system operates.

A family usually consumes their meals at their kitchen table. But the food does not simply appear on the kitchen table. The food has to be delivered to the kitchen table. This process can be described as follows.

Food consists of meat, fish, vegetables, fruits, nuts, and a few other items that are safe to eat. The average family acquires their food from some type of grocery store. From the perspective of one family, the total amount of food in the average grocery store far exceeds the amount of food that one family could eat for many, many years. In this article the "sun" will be used to represent a grocery store.

The family must get the food from the grocery store to their kitchen if they are going to eat their meal at their kitchen table. If one person must manually carry the food from the grocery store to their kitchen then the amount of food that can be carried in one trip will be limited to the total weight that one person can carry. However, if the person has a bicycle then the bicycle can carry more weight from the grocery store to the person's home. If a person has an automobile or truck then this will significantly increase the amount of food that a person can transport in one trip from the grocery store to the person's home. In this article a "solar panel" will be used to represent the transfer of food from the grocery store to a person's home. Bigger solar panels, or more solar panels, will represent more food being transferred at one time.

If the food is perishable then the food must be eaten immediately. Or the food will need to be stored inside a refrigerator. A refrigerator significantly extends the shelf life of perishable food. Although different foods have different shelf lives, the shelf life issue will be not relevant in this article. What is relevant is the size of the refrigerator. If the kitchen only has a very small refrigerator that is 2 feet wide, 2 feet deep, and 2 feet high, then only a relatively small amount of perishable food can be stored in this refrigerator. But if the refrigerator is 3 feet wide, 3 feet deep, and 5 feet tall then it could store a lot more perishable food. If the refrigerator is 4 feet wide, 4 feet deep, and 6 feet tall then it could store even more perishable food. In this article a "12 volt battery" will be used to represent a refrigerator. In this article more batteries will represent a bigger refrigerator or more storage capacity.

Although some food can be eaten fresh, most food will need to be cooked to make the food edible. Some food can be cooked in a frying pan or in a pot on top of a stove, and some food can be baked inside an oven, and some food can be prepared inside a microwave oven. In this article the way the food is cooked will not be relevant. What is relevant is that the food needs to be cooked. In this article it will be assumed that the food is cooked inside an oven and an "inverter" will represent the oven. The size of the inverter (or oven) will determine how much food can be prepared at one time.

The amount of food that should be placed on a kitchen table for one meal will depend on the number of people who will be eating that meal. More people will require more food. In this article "one electrical appliance" will represent one person. Different people require different amounts of food at one meal, and different electrical appliances require different amounts of electricity to operate.
  1. Solar Panels: A solar panel converts the sun's energy into DC electricity. Solar panels are sold based on their size in "watts." A 60 watt solar panel will produce four times more power than a 15 watt solar panel. Bigger solar panels and more solar panels will produce more total power on those days when the sun's rays are reaching the solar panels. Monocrystalline solar panels are recommended. After a good quality solar panel has actually been put into use then the solar panel will normally still produce at least 90% of its original power after 10 years, and it will still produce at least 80% of its original power after 20 years. In other words, a good quality 100 watt solar panel will still produce at least 90 watts after 10 years of service, and it will still produce at least 80 watts after 20 years of service.

  2. Batteries: Batteries are similar to a refrigerator. More batteries will allow you to store more electricity each day when the sun's rays are reaching your location. Some days are overcast with clouds, and on some days it is raining or snowing, and winter days are shorter than summer days. Therefore batteries, just like a refrigerator, are very important for storing power when you cannot immediately replenish your power. The types of batteries that are used in solar systems are deep cycle, or marine, or golf cart batteries because they are designed to provide power over an extended period of time. An automobile or truck battery provides a significant amount of power for a short period of time to start the engine of a car or truck. Then the automobile battery is recharged by the engine. An automobile battery is not designed for a solar power system. In an emergency one or more automobile batteries could be used in a solar power system but an automobile battery cannot be safely discharged as low as a deep cycle battery. And an automobile battery will not last as long in a solar power system. A good deep cycle battery will normally last 5 or 6 or 7 years if it is properly maintained.

    Note: There should also be a "charge controller" between the solar panels and the batteries to prevent the batteries from being overcharged. This would be like trying to put too much food into a refrigerator. The extra food will not fit and this would mean the refrigerator door could not be properly closed and the refrigerator would not work. Overcharging a battery can cause serious problems and it should not be done. That is the purpose of a "charge controller." I recommend an MPPT charge controller.

  3. Inverter: An inverter changes direct current (DC) into alternating current (AC) which is the type of current used by the appliances inside a home. The maximum amount of power an inverter can provide at one time is expressed in watts. Inverters that are plugged into the cigarette lighters in motor vehicles are usually 750 watts or less. The minimum size inverter for a recreational vehicle is 2000 watts. The minimum size inverter for a normal home is at least 3000 watts but 4000 or 5000 watts is much better. I recommend a "pure sine wave" inverter because it will produce power that is compatible with almost all electrical appliances. (Note: Some companies are calling their inverters a "solar generator" but it is still an inverter and it still needs at least one solar panel and at least one battery.)

  4. Electrical Appliances: In the USA almost all inverters create 110 volt power. 110 volt power is also called 115 volt and 120 volt. Even though they are called by different names, they are all the same thing. In the USA most home appliance use 110 volt power. Depending on your application, it may be possible to plug some of your important 110 volt appliances (such as a refrigerator) directly into the inverter when emergency power is needed.

  5. Transformer: Some appliances, such as an electric oven, require 220 volts (also called 230 or 240 volts). A "transformer" will increase 110 volts to 220 volts for these appliances. However, a 220 volt appliance will quickly use up the power that is stored in a set of batteries. Therefore it is not practical to use a solar system to provide power to an electric oven, or an electric clothes dryer, or a central heating and air-conditioning system.
    • 12 volt DC fans, or 110 volt fans, are better options for staying comfortable in hot weather.
    • A few 5-gallon solar shower bags (sold in the camping department of many stores) are a better option for heating water when compared to a hot water tank or an on-demand hot water heater.
    • Propane ovens are better options for cooking.
    • A 700 watt to 900 watt microwave oven is good for heating food and for cooking some types of food.
    • An old-fashioned clothesline and clothespins are a better option for drying clothes.
    However, if you have a 220 volt well pump then it should be used to provide fresh water.
    In summary, unless you have a "real" need for 220 volt power, then a transformer may not be needed for your emergency power system.

    Note: 220 volt power has two 110 volt lines that are synchronized. Although it is possible to acquire two special 110 volt inverters that are properly phased to each other, it is much better to install a 220 volt transformer on your solar power system if you really need 220 volt power.

Conclusion

The purpose of this article was to provide a very, very simple explanation of solar power systems.

If you wish to know a little more about solar power then you can click on the following links and read the articles that I have previously posted on my website.

Alternate Energy Sources - November 1, 2011.

How to Build a Portable Solar Power Generator - December 1, 2005.

Rechargeable Batteries and a Solar Battery Charger - December 20, 2010.

May God Bless,
Grandpappy.

Grandpappy's e-mail address is: RobertWayneAtkins@hotmail.com

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