Battery Charge Controller for Solar System

Introduction

Electricity is the most potential for foundation of economic growth of a country and constitutes one of the vital infrastructural inputs in socio-economic development .The world faces a surge in demand for electricity that is driven by such powerful forces as population growth, extensive urbanization, industrialization and the rise in the standard of living.

Bangladesh, with its 160 million people in a land mass of 147,570sq km. In 1971, just 3% of Bangladesh’s population had access to electricity .Today that number has increased to around 50% of the population –still one of the lowest in the world-but access often amounts to just a few hours each day. Bangladesh claims the lowest per-capita consumption of commercial energy in South Asia, but there is a significant gap between supply and demand. Bangladesh’s power system depends on fossil fuels supplied by both private sector and state-owned power system. After system losses, the countries per installed capacity for electricity   generation can generate 3,900-4300 Megawatts of electricity per day; however, daily demand is near   6,000 Megawatts per day. In general, rapid industrialization and urbanization has propelled the increase in demand for energy by 10% per year. What further exacerbates Bangladesh’s energy problems is the fact the country’s power generation plants are dated and may need to be shut     down sooner rather than later.

There was no institutional framework for renewable energy before 2008; therefore the renewable energy policy was adopted by the government. According to the policy an institution, Sustainable & Renewable Energy Development Authority (SREDA), was to be established as a focal point for the promotion and development of sustainable energy, comparison of renewable energy, energy efficiency and energy conservation. Establishment of SREDA is still under process. Power division is to facilitate the development of renewable energy until SREDA is formed.

While the power sector in Bangladesh has witnessed many success stories in the last couple of years, the road that lies ahead is dotted with innumerable challenges that result from the gaps that exist between what’s planned versus what the power sector has been able to deliver. There is no doubt that the demand for electricity is increasing rapidly with the improvement of living standard, increase of agricultural production, progress of industries as well as overall development of the country.

Power Generation Scenery in Bangladesh

Severe power crisis compelled the Government to enter into contractual agreements for high-cost temporary solution, such as rental power and small IPPs, on an emergency basis, much of it diesel or liquid-fuel based. This has imposed tremendous fiscal pressure. With a power sector which is almost dependent on natural-gas fired generation (89.22%), the country is confronting a simultaneous shortage of natural gas and electricity. Nearly 400-800 MW of power could not be availed from the power plants due to shortage of gas supply. Other fuels for generating low-cost, base-load energy, such as coal, or renewable source like hydropower, are not readily available and Government has no option but to go for fuel diversity option for power generation.

When the present Government assumed the charge, the power generation was 3200 – 3400 MW against national demand of 5200 MW. In the election manifesto, government had declared specific power generation commitment of 5000 MW by 2011 and 7000 MW by 2013.

Over View of Electricity Last Couple of Year

To achieve this commitment, in spite of the major deterrents energy crisis and gas supply shortage, government has taken several initiatives to generate 6000 MW by 2011, 10,000 MW by 2013 and 15,000 MW by 2016, which are far beyond the commitment in the election manifesto. 2944 MW of power (as of Jan, 2012) has already been added to the grid within three years time. The government has already developed Power system Master Plan 2010. According to the Master Plan the forecasted demand would be 19,000 MW in 2021 and 34,000 MW in 2030. To meet this demand the generation capacity should be 39,000 MW in 2030. The plan suggested going for fuel-mixed option, which should be domestic coal 30%, imported coal 20 %, natural gas (including LNG) 25%, liquid fuel 5%, nuclear, renewable energy and power import 20%. In line with the Power system Master Plan 2010, an interim generation plan up to 2016 has been prepared, which is as follows:

Table 01: Plants Commissioned During 2009-2011

Power Generation Sector	2009 (MW)	2010 (MW)	2011 (MW)	TOTAL (MW)
Public	–	255	800	1055
Private	356	270	125	751
Q. Rental	–	250	838	1088
Total	356	775	1763	2894

  *In 2011, 1763 MW commissioned against plan for 2194 MW

Power Generation Units (fuel Type Wise)

Table 02: Installed Capacity of BPDB Power Plants as on April 2012

Plant Type	Total Capacity (in MW)	(%) Percentage in total developed power
Gas	5086.00 MW	75.99 %
HSD	682.00MW	10.19%
HFO	335.00 MW	5.01 %
Coal	250.00MW	3.74%
Hydro	230.00 MW	3.44 %
F.Oil	110.00MW	1.64%
Total	6693.00MW	100%

Table 03: Dreaded Capacity of BPDPB Power Plants as on April 2012

Plant Type	Total Capacity (in MW)	(%) Percentage in total developed power
Gas	4651.00 MW	76.74 %
HSD	657.00MW	10.84%
HFO	248.00 MW	4.09 %
Coal	200.00MW	3.3%
Hydro	220.00 MW	3.63 %
F.Oil	85.00MW	1.4%
Total	6061.00MW	100%

OWNER WISE DALY GENERATION REPORT

Table 04: Daily Generation of 25/04/2012

Owner Name	Derated Capacity(MW)	Day Peak(MW)	Eve. Peak(MW)
PDB	3209.00	1311.00	1516.00
SUB,PDB	223.00	51.00	104.00
EGCB	210.00	80.00	86.00
APSCL	662.00	539.00	567.00
IPP	1260.00	1021.00	1196.00
SIPP,REB	110.00	97.00	81.00
Rental(3 years)	33.00	15.00	0.00
SIPP,REB	215.00	150.00	156.00
Q.Rental 3Years	250.00	162.00	203.00
Rental 15 years	21.00	20.00	13.00
QRPP(5yars)	315.00	136.00	304.00
Others	0.00	49.00	60.00
RPP (3YEARS)	420.00	172.00	281.00
QRPP(3YEARS)	476.00	196.00	198.00
RPP(15YARS)	147.00	125.00	134.00
Total	7551.00	4124.00	4899.00

Table 05: Maximum Generation: Last Six Year

Maximum generation in 2012	6066.00MW as on 22-03-2012
Maximum generation in 2011	5174.00MW as on 23-11-2011
Maximum generation in 2010	4698.50MW as on 20-082010
Maximum generation in 2009	4296.00MW as on 18-09-2009
Maximum generation in 2008	4036.70MW as on 19-09-2008
Maximum generation in 2007	4130.00MW as on 17-09-2007
Maximum generation in history	6066.00MW as on 2908-2011

Electricity Demand and Supply

Per capita generation of electricity in Bangladesh is now about 252KWh. In view of the prevailing low consumption base in Bangladesh, a high growth rate in energy and electricity is indispensable for facilitating smooth transition from subsistence level of economy to the development threshold. The average annual growth in peak demand of the national grid over the last three decades was about 8.5%. It is believed that the growth is still suppressed by shortage of supply. Desired growth is generation is hampered, in addition to financial constraints, by inadequacy in supply of primary energy resources. The strategy adopted during the energy crisis was to reduce dependence on imported oil through its replacement by indigenous fuel. Thus almost all plants built after the energy crises were based on natural gas as fuel. Preference for this fuel is further motivated by its comparatively low tariff for power generation.

 Power Demand Forecasts (2010-2030)

The adoption scenarios of the power demand forecast in this MP are as shown in the figure below.

The figure indicates three scenarios; (i) GDP 7% scenario and (ii) GDP 6% scenario, based on energy intensity method, and (iii) government policy scenario.

FY	Government Policy Scenario		Comparison GDP (7%)                   Scenario		Comparison GDP (6%)        Scenario
	Peak Demand      (MW)	Generation    (GWH)	Peak Demand       (MW)	Generation      (GWH)	Peak Demand    ( MW)	Generation     (GWH)
2010	6454	33922	6454	33922	6454	33922
2011	6765	35557	6869	36103	6756	35510
2012	7518	39515	7329	38521	7083	37228
2013	8349	43882	7837	41191	7436	39084
2014	9268	48713	8398	44140	7819	41097
2015	10283	54047	9019	47404	8232	43267
2016	11405	59945	9705	51009	8680	45622
2017	12644	66457	10463	54994	9165	48171
2018	14014	73658	11300	59393	9689	50925
2019	15527	81610	12224	64249	10255	53900
2020	17304	90950	13244	69610	10868	57122
2021	18838	99838	14249	75517	11442	60640
2022	20443	109239	15344	81992	12056	64422
2023	21993	118485	16539	89102	12713	68490
2024	23581	128073	17840	96893	13416	72865
2025	25199	137965	19257	105432	14167	77564
2026	26838	148114	20814	114868	14979	82666
2027	28487	158462	22509	125209	15848	88156
2028	30134	168943	24353	136533	16776	94053
2029	31873	180089	26358	148928	17768	100393
2030	33708	191933	28537	162490	18828	107207

Table 06: Demand Forecast (3scenario)

Source: Power System Master Plan (PSMP) Study Team

FY- Forecast year*

INSTALLED CAPACITY

NEW GENERATION PLAN OF THE GOVERNMENT (From 2012 to2016) In MW

Power is the precondition for social and economic development. But currently consumers cannot be provided with uninterrupted and quality power supply due to inadequate generation compared to the national demand. To fulfill the commitment as declared in the Election Manifesto and to implement the Power Sector Master Plan 2010, Government has already been taken massive generation, transmission and distribution plan. The generation target up to 2016 is given below:

YEAR	2012	2013	2014	2015	2016	TOTAL
PUBLIC	632MW	1467MW	1660MW	1410MW	750MW	5919MW
PRIVET	1354MW	1372MW	1637MW	772MW	1600MW	6735MW
IMPORT	0	500MW	0	0	0	500MW
TOTAL	1986MW	3339MW	3297MW	2182MW	2350MW	13154MW

Table 07: Power generation addition from 2009-11

     *2894 MW Power Generation addition from January 2009 to December 2011

Government Upcoming Nearest plan

Government has taken short, medium and long term plan. Under the short term plan, Quick Rental Power Plants will be installed using liquid fuels/gas and capable to produce electricity within 12-24 months. Nearly 1753 MW is planned to be generated from rental and quick rental power plants.

Under the medium term plan, initiatives have been taken to set up power plants with a total generation capacity of 7919 MW that is implementable within 3 to 5 years time. The plants are mainly coal based; some are gas and oil based. In the long term plan, some big coal fired plants will be set up, one will be in Khulna South and other will be in Chittagong, each of having the capacity of 1300 MW. Some 300-450 MW plants will be set up in Bibiana, Meghnaghat, Ashugonj, Sirangonj and in Ghorashal. If the implementation of the plan goes smoothly, it will be possible to minimize the demand-supply gap at the end of 2012.

Government has already started implementation of the plan. Total 31,355 Million-kilowatt hour (MkWh) net energy was generated during 2010-11. Public sector power plant generated 47% while private sector generated 53% of total net generation. The share of gas, hydro, coal and oil based energy generation was 82.12%, 2.78%, 2.49% and 12.61% respectively. On the other hand, in FY 2009-10, 29,247 million-kilowatt hour (MkWh) net energy was generated i.e. electricity growth rate in FY 2011 was 7.21% (In FY 2012 (Jul-Dec, 2011) is 13.2%).

Why do we select this project?

Now fuel crises are increasing day by day in worldwide and it impacts on energy sector to produce or generate electricity. Big amount of fuel from total reserved of fuel in our country is used to generate electricity.

Therefore the reserved fuel will be finish in the future. Analysis are thinking to make the strong energy sector with the rentable energy is one of the major part of the renewable energy to produce electricity and that is why we have chosen the solar energy system.

The solar system is constructed with various types of ingredients. But here the battery is the heart of the solar system. The solar energy is not used directly and it is used with the help of the battery because we get very low D.C voltage from the solar panel. Therefore we need to use the battery to store this low D.C voltage which is supplied from the solar panel. In a solar system, the 50% cost is expense for the battery from its total cost. Since the battery is a major part of the solar system and it is charged perfectly by a controller circuit. If the battery is not charged perfectly then the charge capacity will be decreasing in a very short time and it also can be damaged for the overcharging.

We have chosen the battery charge controller system by considering above reason.

An Introduction to Solar Energy

 The interest in renewable energy has been revived over last few year, especially after global awareness regarding the ill effects of fossil fuel burning. Energy is the source of growth and the mover for economic and social development of a nation and its people. No matter how we cry about development or poverty alleviation it is not going to come until lights are provided to our people for seeing, reading and working.

Natural resources or energy sources such as; fossil fuels, oil natural gas, etc. are completely used or economically depleted. Because we are rapidly exhausting, our non-renewable resources, degrading the potentially renewable resources and even threatening the perpetual resources. It demands immediate attention especially in the third world countries, where only scarce resources are available for an enormous size of population. The civilization is dependent on electric power. There is a relationship between GDP growth rate and electricity growth rate in a country.

Clearly, the present gas production capacity in Bangladesh can’t support both domestic gas needs,  as well as wider electricity generation for the country . On September 15^th 2009, the Power Division of the Ministry of Power, Energy  and Mineral Resources of Bangladesh pushed for urgent action to be taken to improve the country’s energy outlook. The Power Division made recommendation such as ceasing gas supply to gas-fired power plants after 2012 to conserve gas reserves for domestic use.

The Government of Bangladesh is actively engaged in energy crisis management. The National Energy Policy has the explicit goal of supplying the whole country with electricity by 2020. Since 1996, the government has allowed private, independent power producer to enter the Bangladeshi market. It is already importing 100 Megawatts of power from India and has negotiated with private companies renting plants to buy power at higher rates.

It is impossible to conceive development of civilization without “Energy”.Densely populated country like Bangladesh can only sustain and progress if only latest energy technologies can be used efficiently. Government of Bangladesh is working towards achieving “Power i.e. Electricity for All” by the year 2020.Bangladesh is one of the most severely affected counties of the World due to climate change and global warming effects.

What Is Solar Energy?

Solar energy is energy that comes from the sun. Every day the sun radiates, or sends out, an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time!

Where does all this energy come from? It comes from within the sun itself. Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The sun generates energy in its core in a process called nuclear fusion. During nuclear fusion, the sun’s extremely high pressure and hot temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. But the helium atom weighs less than the four nuclei that combined to form it. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.

It takes millions of years for the energy in the sun’s core to make its way to the solar surface, and then just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light. Only a small portion of the energy radiated by the sun into space strikes the earth, one part in two billion. Yet this amount of energy is enormous. Every day enough energy strikes the United States to supply the nation’s energy needs for one and a half years!

Where does all this energy go? About 15 percent of the sun’s energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produce’s rain-fall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs.

History of Solar Energy

People have harnessed solar energy for centuries. As early as the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. Over 100 years ago in France, a scientist used heat from a solar collector to make steam to drive a steam engine.

In the beginning of this century, scientists and engineers began researching ways to use solar energy in earnest. One important development was a remarkably efficient solar boiler invented by Charles Greeley Abbott, an American astrophysicist, in 1936.

The solar water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing just before World War 11. This growth lasted until the mid- 1950s when low-cost natural gas became the primary fuel for heating American homes. The public and world governments remained largely indifferent to the possibilities of solar energy until the oil shortages of the 1970s. Today people use solar energy to heat buildings and water and to generate electricity.

Utilization of solar Energy

Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used.

Solar powered electrical generation relies on heat engines and photovoltaic. Solar energy’s uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, day lighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes. To harvest the solar energy, the most common way is to use solar panels.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

There are main two ways we can produce electricity from the sun:

Photovoltaic Electricity – This method uses photovoltaic cells that absorb the direct sunlight just like the solar cells you see on some calculators.

Solar Thermal Electricity – This also uses a solar collector: it has a mirrored surface that reflects the sunlight onto a receiver that heats up a liquid. This heated liquid is used to make steam that produces electricity.

Solar System Descriptions

In today’s climate of growing energy needs and increasing environmental concern, alternatives to the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative is solar energy.

Solar energy is quite simply the energy produced directly by the sun and collected elsewhere, normally the Earth. The sun creates its energy through a thermonuclear process that converts about 650,000,000¹ tons of hydrogen to helium every second. The process creates heat and electromagnetic radiation. The heat remains in the sun and is instrumental in maintaining the thermonuclear reaction. The electromagnetic radiation (including visible light, infra-red light, and ultra-violet radiation) streams out into space in all directions.

Only a very small fraction of the total radiation produced reaches the Earth. The radiation that does reach the Earth is the indirect source of nearly every type of energy used today. The exceptions are geothermal energy, and nuclear fission and fusion. Even fossil fuels owe their origins to the sun; they were once living plants and animals whose life was dependent upon the sun.

Much of the world’s required energy can be supplied directly by solar power. More still can be provided indirectly. The practicality of doing so will be examined, as well as the benefits and drawbacks. In addition, the uses solar energy is currently applied to will be noted.

Due to the nature of solar energy, two components are required to have a functional solar energy generator. These two components are a collector and a storage unit. The collector simply collects the radiation that falls on it and converts a fraction of it to other forms of energy (either electricity and heat or heat alone). The storage unit is required because of the non-constant nature of solar energy; at certain times only a very small amount of radiation will be received. At night or during heavy cloud cover, for example, the amount of energy produced by the collector will be quite small. The storage unit can hold the excess energy produced during the periods of maximum productivity, and release it when the productivity drops. In practice, a backup power supply is usually added, too, for the situations when the amount of energy required is greater than both what is being produced and what is stored in the container.

Methods of collecting and storing solar energy vary depending on the uses planned for the solar generator. In general, there are three types of collectors and many forms of storage units.

The three types of collectors are flat-plate collectors, focusing collectors, and passive collectors.

Flat-plate collectors are the more commonly used type of collector today. They are arrays of solar panels arranged in a simple plane. They can be of nearly any size, and have an output that is directly related to a few variables including size, facing, and cleanliness. These variables all affect the amount of radiation that falls on the collector. Often these collector panels have automated machinery that keeps them facing the sun. The additional energy they take in due to the correction of facing more than compensates for the energy needed to drive the extra machinery.

Focusing collectors are essentially flat-plane collectors with optical devices arranged to maximize the radiation falling on the focus of the collector. These are currently used only in a few scattered areas. Solar furnaces are examples of this type of collector. Although they can produce far greater amounts of energy at a single point than the flat-plane collectors can, they lose some of the radiation that the flat-plane panels do not. Radiation reflected off the ground will be used by flat-plane panels but usually will be ignored by focusing collectors (in snow covered regions, this reflected radiation can be significant). One other problem with focusing collectors in general is due to temperature. The fragile silicon components that absorb the incoming radiation lose efficiency at high temperatures, and if they get too hot they can even be permanently damaged. The focusing collectors by their very nature can create much higher temperatures and need more safeguards to protect their silicon components.

Passive collectors are completely different from the other two types of collectors. The passive collectors absorb radiation and convert it to heat naturally, without being designed and built to do so. All objects have this property to some extent, but only some objects (like walls) will be able to produce enough heat to make it worthwhile. Often their natural ability to convert radiation to heat is enhanced in some way or another (by being painted black, for example) and a system for transferring the heat to a different location is generally added.

People use energy for many things, but a few general tasks consume most of the energy. These tasks include transportation, heating, cooling, and the generation of electricity. Solar energy can be applied to all four of these tasks with different levels of success.

Heating is the business for which solar energy is best suited. Solar heating requires almost no energy transformation, so it has a very high efficiency. Heat energy can be stored in a liquid, such as water, or in a packed bed. A packed bed is a container filled with small objects that can hold heat (such as stones) with air space between them. Heat energy is also often stored in phase-change or heat-of-fusion units. These devices will utilize a chemical that changes phase from solid to liquid at a temperature that can be produced by the solar collector. The energy of the collector is used to change the chemical to its liquid phase, and is as a result stored in the chemical itself. It can be tapped later by allowing the chemical to revert to its solid form. Solar energy is frequently used in residential homes to heat water. This is an easy application, as the desired end result (hot water) is the storage facility. A hot water tank is filled with hot water during the day, and drained as needed. This application is a very simple adjustment from the normal fossil fuel water heaters.

Swimming pools are often heated by solar power. Sometimes the pool itself functions as the storage unit, and sometimes a packed bed is added to store the heat. Whether or not a packed bed is used, some method of keeping the pool’s heat for longer than normal periods (like a cover) is generally employed to help keep the water at a warm temperature when it is not in use.

Solar energy is often used to directly heat a house or building. Heating a building requires much more energy than heating a building’s water, so much larger panels are necessary. Generally a building that is heated by solar power will have its water heated by solar power as well. The type of storage facility most often used for such large solar heaters is the heat-of-fusion storage unit, but other kinds (such as the packed bed or hot water tank) can be used as well. This application of solar power is less common than the two mentioned above, because of the cost of the large panels and storage system required to make it work. Often if an entire building is heated by solar power, passive collectors are used in addition to one of the other two types. Passive collectors will generally be an integral part of the building itself, so buildings taking advantage of passive collectors must be created with solar heating in mind.

These passive collectors can take a few different forms. The most basic type is the incidental heat trap. The idea behind the heat trap is fairly simple. Allow the maximum amount of light possible inside through a window (The window should be facing towards the equator for this to be achieved) and allow it to fall on a floor made of stone or another heat holding material. During the day, the area will stay cool as the floor absorbs most of the heat, and at night, the area will stay warm as the stone re-emits the heat it absorbed during the day. Another major form of passive collector is thermos phonin walls and/or roof. With this passive collector, the heat normally absorbed and wasted in the walls and roof is re-routed into the area that needs to be heated.

The last major form of passive collector is the solar pond. This is very similar to the solar heated pool described above, but the emphasis is different. With swimming pools, the desired result is a warm pool. With the solar pond, the whole purpose of the pond is to serve as an energy regulator for a building. The pond is placed either adjacent to or on the building, and it will absorb solar energy and convert it to heat during the day. This heat can be taken into the building, or if the building has more than enough heat already, heat can be dumped from the building into the pond.

Solar energy can be used for other things besides heating. It may seem strange, but one of the most common uses of solar energy today is cooling. Solar cooling is far more expensive than solar heating, so it is almost never seen in private homes. Solar energy is used to cool things by phase changing a liquid to gas through heat, and then forcing the gas into a lower pressure chamber. The temperature of a gas is related to the pressure containing it, and all other things being held equal, the same gas under a lower pressure will have a lower temperature. This cool gas will be used to absorb heat from the area of interest and then be forced into a region of higher pressure where the excess heat will be lost to the outside world. The net effect is that of a pump moving heat from one area into another, and the first is accordingly cooled.

Besides being used for heating and cooling, solar energy can be directly converted to electricity. Most of our tools are designed to be driven by electricity, so if you can create electricity through solar power, you can run almost anything with solar power. The solar collectors that convert radiation into electricity can be either flat-plane collectors or focusing collectors, and the silicon components of these collectors are photovoltaic cells.

Photovoltaic cells, by their very nature, convert radiation to electricity. This phenomenon has been known for well over half a century, but until recently the amounts of electricity generated were good for little more than measuring radiation intensity. Most of the photovoltaic cells on the market today operate at an efficiency of less than 15%; that is, of all the radiation that falls upon them, less than 15% of it is converted to electricity. The maximum theoretical efficiency for a photovoltaic cell is only 32.3%, but at this efficiency, solar electricity is very economical. Most of our other forms of electricity generation are at a lower efficiency than this.

Unfortunately, reality still lags behind theory and a 15% efficiency is not usually considered economical by most power companies, even if it is fine for toys and pocket calculators. Hope for bulk solar electricity should not be abandoned, however, for recent scientific advances have created a solar cell with an efficiency of 28.2% efficiency in the laboratory. This type of cell has yet to be field-tested. If it maintains its efficiency in the uncontrolled environment of the outside world, and if it does not have a tendency to break down, it will be economical for power companies to build solar power facilities after all.

Of the main types of energy usage, the least suited to solar power is transportation. While large, relatively slow vehicles like ships could power themselves with large onboard solar panels, small constantly turning vehicles like cars could not. The only possible way a car could be completely solar powered would be through the use of battery that was charged by solar power at some stationary point and then later loaded into the car. Electric cars that are partially powered by solar energy are available now, but it is unlikely that solar power will provide the world’s transportation costs in the near future.

Solar power has two big advantages over fossil fuels. The first is in the fact that it is renewable; it is never going to run out. The second is its effect on the environment.

While the burning of fossil fuels introduces many harmful pollutants into the atmosphere and contributes to environmental problems like global warming and acid rain, solar energy is completely non-polluting. While many acres of land must be destroyed to feed a fossil fuel energy plant its required fuel, the only land that must be destroyed for a solar energy plant is the land that it stands on. Indeed, if a solar energy systems were incorporated into every business and dwelling, no land would have to be destroyed in the name of energy. This ability to decentralize solar energy is something that fossil fuel burning cannot match.

As the primary element of construction of solar panels, silicon, is the second most common element on the planet, there is very little environmental disturbance caused by the creation of solar panels. In fact, solar energy only causes environmental disruption if it is centralized and produced on a gigantic scale. Solar power certainly can be produced on a gigantic scale, too. Among the renewable resources, only in solar power do we find the potential for an energy source capable of supplying more energy than is used.

Suppose that of the 4.5×10¹⁷ kWh per annum that is used by the earth to evaporate water from the oceans we were to acquire just 0.1% or 4.5×10¹⁴ kWh per annum. Dividing by the hours in the year gives a continuous yield of 2.90×10¹⁰ kW. This would supply 2.4 kW to 12.1 billion people.

This translates to roughly the amount of energy used today by the average American available to over twelve billion people. Since this is greater than the estimated carrying capacity of the Earth, this would be enough energy to supply the entire planet regardless of the population.

Unfortunately, at this scale, the production of solar energy would have some unpredictable negative environmental effects. If all the solar collectors were placed in one or just a few areas, they would probably have large effects on the local environment, and possibly have large effects on the world environment. Everything from changes in local rain conditions to another Ice Age has been predicted as a result of producing solar energy on this scale. The problem lies in the change of temperature and humidity near a solar panel; if the energy producing panels are kept non-centralized, they should not create the same local, mass temperature change that could have such bad effects on the environment.

Of all the energy sources available, solar has perhaps the most promise. Numerically, it is capable of producing the raw power required to satisfy the entire planet’s energy needs. Environmentally, it is one of the least destructive of all the sources of energy. Practically, it can be adjusted to power nearly everything except transportation with very little adjustment, and even transportation with some modest modifications to the current general system of travel. Clearly, solar energy is a resource of the future.

Advantage of Solar Energy:

1. Technology is easy
2. Affordable cost
3. Within the ability of poor’s
4. Basically no maintenance cost
5. Only source of energy is sunshine
6. Energy source is cost free
7. Environmental Pollution is less
8. No emission
9. Very few materials are required

CHAPTER 03

Theory of solar cell charge Circuit

Equivalent circuit of a solar cell

To understand the electronic behavior of a solar cell, it is useful to create a model which is electrically equivalent, and is based on discrete electrical components whose behavior is well known. An ideal solar cell may be modeled by a current source in parallel with a diode; in practice no solar cell is ideal, so a shunt resistance and a series resistance component are added to the model. The resulting equivalent circuit of a solar cell is shown on the left. Also shown, on the right, is the schematic representation of a solar cell for use in circuit diagrams.

Characteristic equation

From the equivalent circuit it is evident that the current produced by the solar cell is equal to that produced by the current source, minus that which flows through the diode, minus that which flows through the shunt resistor:

I = I_L − I_D − I_SH       

Where

• § I = output current (amperes)
• § I_L = photo generated current (amperes)
• § I_D = diode current (amperes)
• § I_SH = shunt current (amperes).

The current through these elements is governed by the voltage across them:

V_j = V + IR_S

Where

•  V_j = voltage across both diode and resistor R_SH (volts)
•  V = voltage across the output terminals (volts)
•  I = output current (amperes)
•  R_S = series resistance (Ω).

By the Shockley diode equation, the current diverted through the diode is:

Where

•  I₀ = reverse saturation current (amperes)
• n = diode ideality factor (1 for an ideal diode)
•  q = elementary charge
•  k = Boltzmann’s constant
•  T = absolute temperature
• At 25°C,  volts.

By Ohm’s law, the current diverted through the shunt resistor is:

Where

• § R_SH = shunt resistance (Ω).

Substituting these into the first equation produces the characteristic equation of a solar cell, which relates solar cell parameters to the output current and voltage:

An alternative derivation produces an equation similar in appearance, but with V on the left-hand side. The two alternatives are identities; that is, they yield precisely the same results.

In principle, given a particular operating voltage V the equation may be solved to determine the operating current I at that voltage. However, because the equation involves I on both sides in a transcendental function the equation has no general analytical solution. However, even without a solution it is physically instructive. Furthermore, it is easily solved using numerical methods. (A general analytical solution to the equation is possible using Lambert’s W function, but since Lambert’s W generally itself must be solved numerically this is a technicality.)Since the parameters I₀, n, R_S, and R_SH cannot be measured directly, the most common application of the characteristic equation is nonlinear regression to extract the values of these parameters on the basis of their combined effect on solar cell behavior.

 Basic Battery Charging Methods

Constant Voltage a constant voltage charger is basically a DC power supply which in its simplest form may consist of a step down transformer from the mains with a rectifier to provide the DC voltage to charge the battery. Such simple designs are often found in cheap car battery chargers. The lead-acid cells used for cars and backup power systems typically use constant voltage chargers. In addition, lithium-ion cells often use constant voltage systems, although these usually are more complex with added circuitry to protect both the batteries and the user safety.

Constant Current Constant current chargers vary the voltage they apply to the battery to maintain a constant current flow, switching off when the voltage reaches the level of a full charge. This design is usually used for nickel-cadmium and nickel-metal hydride cells or batteries.

Taper Current this is charging from a crude unregulated constant voltage source. It is not a controlled charge as in V Taper above. The current diminishes as the cell voltage (back emf) builds up. There is a serious danger of damaging the cells through overcharging. To avoid this charging rate and duration should be limited. Suitable for SLA batteries only.

Pulsed charge Pulsed chargers feed the charge current to the battery in pulses. The charging rate (based on the average current) can be precisely controlled by varying the width of the pulses, typically about one second. During the charging process, short rest periods of 20 to 30 milliseconds, between pulses allow the chemical actions in the battery to stabilize by equalizing the reaction throughout the bulk of the electrode before recommencing the charge. This enables the chemical reaction to keep pace with the rate of inputting the electrical energy. It is also claimed that this method can reduce unwanted chemical reactions at the electrode surface such as gas formation, crystal growth and passivation. (See also Pulsed Charger below). If required, it is also possible to sample the open circuit voltage of the battery during the rest period.

Burp charging also called Reflex or Negative Pulse Charging Used in conjunction with pulse charging, it applies a very short discharge pulse, typically 2 to 3 times the charging current for 5 milliseconds, during the charging rest period to depolarize the cell. These pulses dislodge any gas bubbles which have built up on the electrodes during fast charging, speeding up the stabilization process and hence the overall charging process. The release and diffusion of the gas bubbles is known as “burping”. Controversial claims have been made for the improvements in both the charge rate and the battery lifetime as well as for the removal of dendrites made possible by this technique. The least that can be said is that “it does not damage the battery”.

IUI Charging this is a recently developed charging profile used for fast charging standard flooded lead acid batteries from particular manufacturers. It is not suitable for all lead acid batteries. Initially the battery is charged at a constant (I) rate until the cell voltage reaches a preset value – normally a voltage near to that at which gassing occurs. This first part of the charging cycle is known as the bulk charge phase. When the preset voltage has been reached, the charger switches into the constant voltage (U) phase and the current drawn by the battery will gradually drop until it reaches another preset level. This second part of the cycle completes the normal charging of the battery at a slowly diminishing rate. Finally the charger switches again into the constant current mode (I) and the voltage continue to rise up to a new higher preset limit when the charger is switched off. This last phase is used to equalize the charge on the individual cells in the battery to maximize battery life. See Cell Balancing.

Trickle charge Trickle charging is designed to compensate for the self discharge of the battery. Continuous charge. Long term constant current charging for standby use. The charge rate varies according to the frequency of discharge. Not suitable for some battery chemistries, e.g. NiMH and Lithium, which are susceptible to damage from overcharging In some applications the charger is designed to switch to trickle charging when the battery is fully charged.

Float charge. The battery and the load are permanently connected in parallel across the DC charging source and held at a constant voltage below the battery’s upper voltage limit. Used for emergency power back up systems. Mainly used with lead acid batteries.

Random charging All of the above applications involve controlled charge of the battery, however there are many applications where the energy to charge the battery is only available, or is delivered, in some random, uncontrolled way. This applies to automotive applications where the energy depends on the engine speed which is continuously changing. The problem is more acute in EV and HEV applications which use regenerative braking since this generates large power spikes during braking which the battery must absorb. More benign applications are in solar panel installations which can only be charged when the sun is shining. These all require special techniques to limit the charging current or voltage to levels which the battery can tolerate.

Charge controller

A charge controller, charge regulator or battery regulator limits the rate at which electric current is added to or drawn from electric batteries.  It prevents overcharging and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. It may also prevent completely draining (“deep discharging”) a battery, or perform controlled discharges, depending on the battery technology, to protect battery life.   The terms “charge controller” or “charge regulator” may refer to either a stand-alone device, or to control circuitry integrated within a battery pack, battery-powered device, or battery recharger.

Charge controllers are sold to consumers as separate devices, often in conjunction with solar or wind power generators, for uses such as RV, boat, and off-the-grid home battery storage systems.   In solar applications, charge controllers may also be called solar regulators.  

A series charge controller or series regulator disables further current flow into batteries when they are full. A shunt charge controller or shunt regulator diverts excess electricity to an auxiliary or “shunt” load, such as an electric water heater, when batteries are full.  

Simple charge controllers stop charging a battery when they exceed a set high voltage level, and re-enable charging when battery voltage drops back below that level. Pulse width modulation (PWM) and maximum power point tracker (MPPT) technologies are more electronically sophisticated, adjusting charging rates depending on the battery’s level, to allow charging closer to its maximum capacity Charge controllers may also monitor battery temperature to prevent overheating. Some charge controller systems also display data; transmit data to remote displays, and data logging to track electric flow over time.

Circuitry that functions as a charge regulator controller may consist of several electrical components, or may be encapsulated in a single microchip, an integrated circuit (IC) usually called a charge controller IC or charge control IC

Charge controller circuits are used for rechargeable electronic devices such as cell phones, laptop computers, portable audio players, and uninterruptible power supplies, as well as for larger battery systems found in electric vehicles and orbiting space satellites^. Charge controller circuitry may be located in the battery-powered device, in a battery pack for either wired or wireless (inductive) charging, in line with the wiring,or in the AC adapter or other power supply module.

CHAPTER 04

Design and Operation

 

Working principal of Solar Charge Controller:

The overall circuit can be divided by the following major parts:

1. IC SG 3524
2.  IC LM358
3. Relay
4. MOSFET
5. Input/output Ports

The working principles of those major parts are provided below:

1. IC- SG 3524: This is the heart of the controller circuit. The IC has 16 numbers of pins.

• The Pin numbers 1 and 9 are mainly used for the controlling purpose.
• The Pin numbers 6 and 7 work as a Pulse Width Modulator.
• The Pin numbers 4, 5 and 8 used for grounding purpose.
• The Pin number 11 and 14 are used to MOSFET triggering.
• The Pin numbers 12, 13 used as collector.
• The Pin numbers 2, 3, 10 and 16 not in used.
• The Pin number 15 used to input voltage.

Here a 10k variable resister is used to increase and decrease the width of the pulses.

If the width of the pulse is increased then current becomes high current will be low when the width of the pulse is decreased.

1. IC-LM 358: This is an Operational Amplifier IC used to general purpose of amplification. The IC has 8 numbers of pins.

• The Pin number 1 provides the desire outputs to the relay unit.
• The Pin number 2 get constant supply 5.1 volts from zener diode.
• The Pin number 3 used as non inverting input.

Here a 10K variable register is used to select the value of the changing voltage.

Relay Unit: The relay of 12V DC which maintains a very important role for charge controlling. The magnetic contact of the relay energized when is depending with the charging period of OFF-ON. If charge is decreased then it becomes ON with the help of magnetic contact. If the battery is fully charged then it goes into the OFF mode. The diode IN4007 is used across the relay to defuse the back emf which is produced in the relay. It is very important for protection the relay.

 MOSFET: Here two N-channel MOSFET have been used because we are controlling the (-ve) terminal of the circuit. These two MOSFET are used to get higher current in the circuit. It is not possible to use more than two MOSFET because the pins 14N0 and 11N0 of I.C SG3524 are triggering the gate of MOSFET. There is a 10k variable resistor in this MOSFET which is used to select the max rating of the battery.

 Input/output Port: There are three ports in this circuit which are as follows:

1. Solar Input Port
2.  Battery Output Port
3. DC Output Port

A very small amount of current produce in the solar cells when sun light hit the panel. The charging circuit collects those current by the solar input port.

The negative of the DC which controlled by the charging circuit meets with the negative of the battery output port. On the other side positive of the DC connected with the positive of the batter output port.

The battery output port provides the conventional DC to the battery. The DC output port provides   12 volts DC supply.

Solar Charge Controller Circuit Rating

Maximum Power	12.5 Watts
Maximum Power Voltage	21 Volts
Maximum Power Current	0.6 Ampere
Short Circuit Current	1.02 Ampere
Open Circuit Voltage	24.6 Volts
Operating Temperature	40—C

Required apparatus:

1. IC-SG3524

2. IC-LM358

3. Relay D.C (12v)

4. Transistor (NPN) B.C547

5. Zener diode 5.1v

6. Diode

* 1N4007, 1N5408

7. Variable resistor 10K

8. Capacitor

* 10µF, 1 µF

9. Resistor

* 1K, 10K , 100K, 47K, 22K, 150K

IC-SG3524:  

INVERT INPUT	1				16	VREF
NON-INV INPUT	2				15	VIN
OSC OUTPUT	3				14	EMITTER B
(+)CL SENSE	4				13	COLLECTOR B
(±)CL SENSE	5				12	COLLECTOR A
RT	6				11	EMITTER A
CT	7				10	SHUTDOWN
GROUND	8				9	COMPENSATION

 

 

 

 

 

 

 

DESCRIPTION

This monolithic integrated circuit contains all the control circuitry for a regulating power supply inverter or switching regulator. Included in a 16-pin dual-in-line package is the voltage reference, error amplifier, oscillator, pulse-width modulator, pulse steering flip-flop, dual alternating output switches and current-limiting and shut-down circuitry. This device can be used for switching regulators of polarity, transformer-coupled DC-to-DC converters, transformer less voltage doublers and polarity converters, as well as other power control applications. The SG3524 is designed for commercial applications of 0C to +70C.

FEATURES

Complete PWM power control circuitry

Single ended or push-pull outputs

Line and load regulation of 0.2%

1% maximum temperature variation

Total supply current is less than 10mA

Operation beyond 100 kHz

Description

The LM385 is a general purpose op-amp with 2 channels.

Applications include transducer amplifiers, dc amplification blocks, and all the conventional operational amplifier circuits that now can be implemented more easily in single-supply-voltage systems. For example, these devices can be operated directly from the standard 5-V supply used in digital systems and easily can provide the required interface electronics without additional ±5-V supplies

3. Relay D.C (12v) & Transistor (NPN) B.C547

Description

A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal.

Description

BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is commonly used to amplify current. A small current at its base controls a larger current at collector & emitter terminals.

BC547 is mainly used for amplification and switching purposes. It has a maximum current gain of 800. Its equivalent transistors are BC548 and BC549.

The transistor terminals require a fixed DC voltage to operate in the desired region of its characteristic curves. This is known as the biasing. For amplification applications, the transistor is biased such that it is partly on for all input conditions. The input signal at base is amplified and taken at the emitter. BC547 is used in common emitter configuration for amplifiers. The voltage divider is the commonly used biasing mode. For switching applications, transistor is biased so that it remains fully on if there is a signal at its base. In the absence of base signal, it gets completely off.

5. Zener diode 5.1

Description:

A Zener Diode is a special kind of diode which permits current to flow in the forward direction as normal, but will also allow it to flow in the reverse direction when the voltage is above a certain value – the breakdown voltage known as the Zener voltage. Zener diodes are useful for creating a reference voltage or as a voltage stabilizer for low-current applications. These diodes are rated for 5.1 volts with a maximum of 1W. Price is for a single diode.

6. Diod 1N4007:

General Purpose Rectifier

Features

* Low forward voltage drop.

* High surge current capability.

 

7. Variable resistor 10K

Features:

*Power: 1/4W

*Resistance: 10K Ohm

*10K oHm Trimmer , Variable Resistors/ Trim pot Potentiometer

    8. Capacitor 10µ, 1µ:

A capacitor is a passive electronic component that stores energy in the form of an electrostatic field. In its simplest form, a capacitor consists of two conducting plates separated by an insulating material called thedielectric. The capacitance is directly proportional to the surface areas of the plates, and is inversely proportional to the separation between the plates. Capacitance also depends on the dielectric constant of the substance separating the plates

1.       Resistor: