Study - 2

• 2. Investment and value for money

Either using the UPS or solar energy, I would pay a considerable sum of money, but I need to study both cases well.

At first I have to decide upon what load I want to have powered without any downtime due to power shortage. I began with a very big fancy dream of powering all my apartment without downtime. That means that I need enough power for all the electrical appliances for at least 1.5 Hr daily. With a simple calculation, I consume an average of 250 kWh monthly and I will assume I use them in the period of 6 hours daily. Therefore my month will have 26 days (because of weekends) x 6 Hr = 156 hours of electrical usage a month. that means that I need an average net power output about 1.6 kW, and I need it for 1.5 Hr.

In Egypt the voltage reaching domestic areas for home usage is 220 V AC. That means that I need a current of  1600 Watt / 220 V AC = 7.3 Amperes. Converting the voltage to 12 V DC (which is the batteries' voltage that I assume to use either in the UPS or solar energy system), therefore the current rises to about 133 Amperes (that is calculated by dividing the required power 1600 Watt by 12 V DC, because the power is constant). This is roughly calculated because both systems have losses which will be discussed later.

Assuming that I need this power for 1.5 Hr, therefore I need a power storage of 133 x 1.5 = 200 Amperes.

UPS

A typical UPS of 2000 VA = 1200 Watt has two batteries of  12 V DC, 9 Ah. That's a total of 18 Ah.

Dividing 18 Ah by 133 Ah, the UPS battery will be completely consumed in about 8 minutes (taking into consideration that batteries should never be completely discharged, I will assume it will be discharged to 30% then the power will cutoff, I will only have about 5 minutes.

That UPS from GE (pure sine wave) will cost me 840$ = 5880EGP + 30% customs and shipping = 7644 EPG, and the surprise is that is not enough to power my full load, but that is the nearest one I could get a price for. By common sense, the sufficient UPS (from power output perspective, not from time perspective) will cost me at least 1000$ = 7000 + 30% = 9100EGP .

I certainly can get extra batteries to prolong the time for working in power outage. I will need 133 Ah plus taking into consideration that I will keep the batteries charged above 50% (to prolong their lifetime), I will need a battery bank of 266 Amperes for every hour of power outage (in my assumption of 1.5 Hr, I will need 400 Ah) This will cost me an extra of 2000 EGP per 100 Ah (batteries type are either Trojan or Bosch). The system cost will reach about 17100 EGP. (that's a big sum of money).

The second noticeable thing is that all the stored power inside batteries is charged from my grid and is not free.

Another important point to be taken into consideration that the battery charger built in the UPS has a maximum charging current, and that affects the charging time of the batteries. My example UPS  claims to have a recharge time of 6 Hrs. By calculation, my 400 Ah batteries will need (400 Ah / 18 Ah) x 6 Hr = 133 hours. In this case, I can use my UPS with the large battery bank once or twice a week.

to be continued...

Study - 1

After having defined the problem, I had to study the alternatives for solutions. I had several solutions to think about, the first of them is to do NOTHING :). This way I will save the cost for my backup system, the time to study and implement it and also I will not pay for the time when I used no electricity.
My engineering hunger didn't left me do so, unfortunately.
So I had to think about UPS to power my devices for the power outage time. It will cost much for a big enough UPS and will need batteries replacement every about 3 years. It charges from electricity (the grid), but it is a tested and proven solution with plug and play feature.
Second thing I thought about is to use renewable energy source as my UPS system. It will also require also enough batteries (which needs replacement every 4-5 years) for powering my devices for the power outage time. It will require another hardware that will cost in total more that an equivalent UPS. It is not considered a plug and play like the UPS, and it charges for free
Solar energy and wind energy were the available and feasible solutions to use. Knowing the fact that wind is not too much in my area, and also knowing that sun is shining almost all year round, then solar energy will have a plus.

I can do a small comparison according to criteria as follows:

• 1. Feasibility

UPS is used mostly to save a backup power for PCs or lighting. To be able to power a fan, AC or any inductive load, I need to get a true sine wave output UPS, which is more expensive in contrast to square wave output or modified sine wave output.

Solar energy also will need a power inverter to change the DC voltage from the panels to AC voltage to power my normal home appliances. Also power inverters' output is divided into square wave, modified sine wave and pure sine wave.

So, both systems are applicable and can be inline with my goal. Also both systems can supply enough power to my target appliances as I will discuss later.

What are the available wave forms?

Most of PCs and devices have power supply that change AC to DC and can take square wave or modified sine wave without problems. Other devices like fans and pumps can also be powered using square wave or modified sine wave, but they will draw much power, heat much more, buzz much louder and shorten their lifetime. Devices like TVs can have distorted image.

Switching on the blog lights

I'm Ahmed Amer, and I live in Cairo, Egypt. I'm holding a BSc in electrical engineering and I'm willing to change the world around me, even within a small radius. If it wasn't for my limited resources, I would've built a far bigger project, but I will go with what I can afford. I'm doing this research to help people looking for the same idea, and I hope people who have experience can help me too.

Problem description:

• 1. Cost 
  

Electrical energy cost in Egypt has been raised at the beginning of 2013 for about 15% according to the following list:
1 EGP = 100 Pt
1 USD = 7 EGP (Today)
Monthly usage up to 50 kWh: Rate is 5 Pt / kWh
Monthly usage up to 200 kWh: Rate is 12 Pt / kWh
Monthly usage up to 350 kWh: Rate is 19 Pt / kWh
Monthly usage up to 650 kWh: Rate is 29 Pt / kWh
Monthly usage up to 1000 kWh: Rate is 53 Pt / kWh
Monthly usage more than 1000 kWh: Rate is 67 Pt / kWh

I took into consideration that the dollar price will not stop rising in the near future.
I took into consideration also that our economy is not growing in the near future, thus buying fuel for power stations puts a great headache on the country's income.
New fuel prices (higher) will be applied by the end of 2013 which shall raise the prices of everything.
My average usage of power lies between 200 and 350 kWh/month, thus I pay between 30 to 70 EGP/month, (which is not too much, but cost was not the main problem). That because i took some steps in saving energy which I will discuss later.

• 2. Availability
  

Normally in winter, there are few power outages, because we have a moderate climate and don't usually use heaters. But in summer, the power outage is frequent (daily) and during the coming 5-7 years, Ramadan month is coming in the summer, where a peak electricity usage occurs during Iftar period which is at dusk. With all those lights on, ACs, TVs, electric stoves, kitchen machines, dish receivers and PCs, the power outage due to load shedding becomes more frequent and lasts longer. In summer it is very hot at 6-7-8-9, where we suffer a lot if there isn't at least a fan to give some breath.

• 3. Appliances switching
  

When the power outage has ended, some of the left-on devices keep their last state, thus going on again as soon as power has been restored. This definitely shortens the device age. In some areas, the power does fluctuate until it is stable again. This includes overvoltage and undervoltage which if the power supply of the device can't handle, it will be damaged. Also motors and pumps can suffer damage from this behavior.

• Environment
  

Extracting power from fossil fuel causes a lot of damage for the environment in the form of increased carbon emissions, thus increases the global warming due to green house effect. In Egypt, the idea of saving the environment is not very popular due to the level of education and poverty, but as a collage-degree holder, I should put that into consideration.

• Social responsibility
  

Well, saving some kilowatts from my side does mean that some poor guys living in a small rooms with one lamp in each room can use this extra power that I saved. A small contribution for the community is better than nothing at all.