Energy storage system is of essence for Solar PV systems?

Energy storage is a vital element in power sector particularly when a country has large volume of Renewable Energy (RE). Cheap, practical and easily available energy storage systems can address some of the critical issues associated with RE sources particularly the Solar PV systems. It will build an atmosphere of confidence in the Utility working, particularly utilities with large scale RE penetration; reduce the investment in transmission systems and development of reserve capacity. 

Widespread deployment of battery storage would mitigate the intermittency phenomenon associated with solar PV systems. In fact, in some of the countries utilities have mandated that all new PV systems should have energy storage systems to smoothen the power variations. Solar PV systems with battery storage could also help to manage unplanned voltage fluctuations, particularly in areas with high penetration of solar PV systems.

Figure 1 shows the main components of a simple Roof top Solar PV system with Battery back up.

Fig.1: Layout of a simple Roof top Solar PV system with Battery back-up

Example of Energy Storage at the Utility end:

Utilities too have promoted Energy Storage systems at their end. Duke Energy has installed a hybrid energy storage system comprising of battery bank and ultra-capacitor at its North Carolina based substation (www.technologyreview.com). In this hybrid storage system, the ultra-capacitor helps the power system during large but short duration power surges, for example when the Solar output dips during a cloudy day. Battery bank, as customary, will help to recover during large duration shortages. 

It is expected that the two storage systems along with smart electronic controls will help the power system in mitigating the power shortage over periods ranging from seconds to several hours. This hybrid storage is supposed to provide a more economical solution as compared to each of the storage systems when used separately. 

According to officials at Maxwell Technologies, the ultra-capacitor storage system can completely eliminate the output fluctuation of less than 30 seconds and provide sufficient smoothening of fluctuations of up to 5 minutes. In recent years the ultra-capacitor energy storage systems have become more accepted as high power shock absorbers for industrial and transportation applications in combination with Lead-acid batteries or advanced chemical batteries. Ultra-capacitor has high power capability due to very low internal resistance, wide operating temperature range of -40^oC to 65^oC, minimum maintenance, high cycling ability and reasonable price.

The latest utility scale battery storage technology emerged in the commercial market is the 8 MWh capacity Vanadium Redox Battery bank installed at Everett Sub-station, Washington state, and which is to be commissioned in January 2017. This battery system,  compact and concealed in container, is non-flammable and can be discharged upto 100%, i.e. the Depth of Discharge (DoD) can be 100%.    

Essence of Energy Storage to End User:

At the end user level the energy storage system will provide the user with the much needed back up during night hours when the grid is out. In countries like India the Time-of-Day (TOD) tariff is not implemented in the residential and commercial sector. I am sure that in the near future Utilities have to come up with the TOD tariff in these sectors also. Then in such a case a solar PV system with energy storage will be very beneficial. 

TOD tariff is an effective tool to reduce the peak hour kWh shortage. Shifting of some portion of the load to the storage system will be of great relief to the utilities reeling under stress. 

Fig 2: A Roof Top Solar PV system with battery back-up.

In some countries, the feed-in-tariff has been rigorously cut down or eliminated at all. In such a condition, the pay back periods of solar PV systems are highly dependent on the percentage of solar energy used for “self-consumption”. 

"Experts are in the opinion that a solar PV system is worth only if the self-consumption is about 50% or more." 

Energy storage systems enable owners of solar PV systems to increase their self-consumption. Although installing energy storage system increases the overall cost of the system and hence the electricity produced, but still it is not as expensive as many would think of. Lithium-ion batteries are considered as the most affordable and dependable energy storage systems. These batteries can discharge bigger burst of power and can eliminate the need of ultra-capacitor but are costly.

Chemical compounds for Electrical Earthing

An electrical installation may face –

1.       Damage because of Lightening,

2.       Electrical leakage,

3.       Short circuit between phases or between phase and neutral,

4.       Surges in the supply.

The above causes may lead to electric fire causing loss of property and loss of human lives. 

Equipments with electronic circuits/PCBs/electronic cards are liable to get damaged due to high neutral currents and unbalanced voltages. Therefore, the voltage between neutral and earth point of any installation should be kept to a minimum. 

Why Earthing or Grounding is needed?

A well designed Earthing or Grounding system is very essential for any electrical installation. All the equipment casings, and neutral of the 3-phase system have to be kept at zero or ground potential. It avoids dangers associated with fault currents; protects both the equipment and the operator against hazardous voltages. 

Whenever there is an insulation failure, there is a tendency that some metallic parts are also energized to the potential of the current carrying part, unless the equipment is effectively earthed. The tolerable value of current through any human being is less than 100 micro-amps. The impact of current flow in a human depends upon the magnitude of current, duration of current flow, and nature of current. Current flow may cause muscular contraction, respiratory nerve blockage, and burning. The most severe is the stopage of heart beat resulting in immediate end of blood circulation. 

A good earthing system protects the installation and equipment by providing low impedance path to fault currents. It also minimizes electromagnetic noise thus preventing unwanted interference with communication signals.

Recommended Values of Earth Resistance:

 The recommended values of earth resistance for various installations are as under:

1. Large sub-station, generating stations etc less than 1 Ohm,
2. Transmission sub-stations, primary distribution sub-stations, large industries; 1 to 5 Ohm,
3. Sub-stations and equipments below 10 kV; 5 to 10 Ohm.

In any case the value of earthing should not exceed 25 Ohm. 

Limitations of  Common Salt and Charcoal when used in an Earthing system:

Resistivity of Soil is important in earthing. It depends on the soil nature, moisture, temperature and content. Clay and black cotton soil have low resistivity as compared to red or rocky soil.

Traditionally we have used charcoal and salt in the earthing pit to reduce the earth/soil resistivity. The common salt is a known corrosive electrolyte which decays the pipe and the conductor used for earthing leading to inconsistent resistive values. Similarly, the soft coke and charcoal used to become ash due to the heavy heat generated by large fault currents in the system, particularly at high voltages.

Recent trend is using Chemical Compounds: 

Now a day advanced chemical compounds are used in the earthing system which lowers the contact resistance of earth electrode significantly (approximately over 60%). It offers low impedance to surges resulting in faster energy dissipation. The earthing system can fail because of inadequate dissipation of heat. These chemical compounds have a high melting temperature of 2500^oC and thus helps in dissipating the heat generated due to faults.

These chemicals or mixtures have excellent shelf life, require no maintenance and do not adversely affect soil or ground water. These compounds have very good performance even during dry weather as its working does not require continuous presence of water.

These chemical compounds for earthing, mainly consisting of Aluminum Silicate, are available in easy carry bags of 10/25/50 kg. Its resistivity is less than 0.1 ohm-m. The key features of these compounds are:

1. Absorbs and retains the moisture for long time; in fact they have the property to absorb water 15 times of its weight,

2. Reduces soil resistivity,

3. Keeps the earth resistance same over a wide temperature variations,

4. Dissipate fault currents at a faster rate,

5. Eliminate the need of salt and charcoal around the electrode,

How to reduce the Electrical Energy consumed by a Lighting System?

Last Updated 20 January 2017

Use of Electrical energy and its costs can be significantly reduced by installing energy efficient lighting system. Efficient building lighting systems use less energy than the systems in place in many of the houses, offices, schools, municipal buildings, stores, and plants. New energy-efficient lighting systems also provide better lighting quality and hence improve the working environment.

How to reduce the Electrical Energy consumed by a Lighting system?

Electrical energy consumed by a lighting system can be reduced either by reducing the lighting power or by reducing the time of use. Operating hours can be reduced by:

1.       Switching,

2.       Occupancy sensors,

3.       Scheduling controls, or

4.       Photocells.

How switching of a Lighting system helps the user?

Switching off the lighting system when not in use reduces the electricity bill and enhances the lamp life. For example, turning of fluorescent lights save energy and extends overall lamp life. Fluorescent lamps will run more hours if operated continuously, but they will last for many more years if they are turned off when not in use. Although the average rated life of fluorescent lamp is shortened by switching, calendar life is lengthened. The period, in hours or years, between the lamp changes is called Calendar life.

"For example, a standard F40 rapid-start lamp operated continuously result in a rated lamp life of 34,000 hours (calendar life of 34,000/8760 = 3.9 years). Turning off these lamps for 12 hours a day or because of approximately 2830 switching, the average rated life of the lamp is reduced to 30,000 hours, but the calendar life is extended to 6.8 years."

Occupancy Sensors reduces the Energy consumed:

Occupancy recognition is the strategy applied to intermittently occupied areas to automatically turn off the lights after the room is left unoccupied. The two principal technologies used for occupancy sensors are -

1)      Passive infra red (PIR) and,

2)       Ultrasonic techniques.

PIR sensors react to body heat and sense occupancy by detecting the difference in heat from a body and the background. Ultrasonic sensors are volumetric detectors and transmit waves above the range of human hearing, then measure the time for the waves to return. Ultrasonic units can detect persons behind obstructions. Sensitivity adjustments are also there to make an ultrasonic unit more or less sensitive to motion. Similarly delay adjustment sets the time the lights remain on when no occupancy is detected. Care should be taken as too short delay can reduce the lamp life and increase occupant complaints.

What is Scheduling Strategy?

Scheduling is a control strategy employed to activate, switch-off, or adjust lighting according to a pre-determined schedule. It is best suited for facilities where majority of activities happen at certain times. Time clocks are the easiest way to implement scheduling strategies and several types of time clocks are available in the market; viz. preset, electromechanical, electronic and astronomical. Astronomical time clocks are used to control outdoor lighting and can automatically adjust sunrise and sunset times. Programmable timer switches can switch lighting loads on-off several times during a day. They have the provision of removing selected days from the schedule and the same can be repeated each week.

Fig : A digital timer switch in circuit.

How Photocells helps in reducing Energy Consumption?

Photocells, made of cadmium-sulphide, are light activated switches used to turn off lights when daylight is adequate for safety and task performance. A delay feature prevents rapid operation during cloudy days.       

Thus, opportunities of energy saving through operational changes and better house-keeping must be identified as it the need of the hour. The short term and cost effective measures should be implemented immediately.  

How Important is an Energy Manager?

Meaning of Energy Management:

Before knowing who the Energy Manager is and what is his or her role lets us understand the meaning of Energy management and importance of energy efficiency.

The term 

" Energy Management " means an effective and judicious use of energy to maximize profits or to minimize the cost. 

 It simply means cutting out the waste by making the best possible use of energy consumed.

How important is Energy Efficiency and Energy Management?

Energy efficiency is very important to all organizations, particularly to energy intensive units and organizations. Organizations looking for more financial returns opt for superior energy management and continuously and effectively work towards improving their energy efficiency. A sound energy management system is a pre-requisite for identifying and implementing energy conservation measures, and sustaining the momentum.

Need for Energy Manager:

Leading organizations appoint Energy Manager and form a dedicated energy management team to establish the energy management programme. So the responsibility for the overall management of energy in its widest contexts is focused formally on the Energy Manager. The tasks of Energy manager are:

•  setting goals, 
• tracking progress, and
• promoting energy management programme. 

It is his or her duty to optimize energy usage within the total limits of his/her specified area.

To be really effective, the Energy Manager requires….

Successful Energy Manager very well understands how energy management helps the organization to achieve its financial and environmental goals.

To be really effective the energy manager requires:

• a broad education,
• vision, 
• imagination, 
• experience, and 
• common sense. 

The traditional Energy Manager has been primarily focused on the energy conservation aspects. As a result their responsibilities were limited to finding Energy Conservation Opportunities (ECOs) performing economic evaluations and submitting proposals to the management.

In addition to the above requirements, today’s Energy Manager must take on a much broader responsibility to accomplish the objectives of an energy management programme. The present generation of Energy Managers may have had a formal training and education in the inter-disciplinary subject of energy management. They may have been trained as engineers in their respective courses and have been exposed, to a greater or lesser extent, to a number of the disciplines which are fundamental to energy management. Today’s Energy Manager must understand financial and physical risk management and be able to evaluate corporate energy risk regarding reliability and energy cost.

Good Convincing Ability:

Energy Manager must be able to convince the benefits of their programs to top management. He or she might find themselves dealing with:

• engineers, 
• financial planners, 
• accountants, 
• supervisors, 
• public relation specialists, 
• government officials, 
• lawyers, 
• journalists etc. 

A good Energy Manager must be able to communicate clearly and persuasively with all those people.

Position of an Energy Manager:

If the objectives of energy management are to be achieved, the Energy Manager must have the authority and direct say into the day-to-day decision making. Depending on the size of the organization, the Energy Manager’s role can be a full time position or an addition to other responsibilities.

The location of the energy manager, whether performed by a single Energy Manager or a number of middle level managers, usually resides somewhere in the organization between senior management and those who control the end-use of energy.

Responsibilities of an Energy Manager and the Team:

Responsibilities and the duties assigned under the Energy Conservation Act 2001, to the Energy Manager and the team are:

1.     Make an annual activity plan with detailed financial investment information to control and   reduce energy costs.

2.      Establish an energy conservation cell within the organization.

3.  To check the efficiency of equipments and to compare with standard energy efficient equipments.

4.  To spread energy awareness among other staff members, conduct internal workshops and distribute the informative materials.

5.     To provide regular training to operative staff.

6.    To collect right information about energy saving from market and from Energy Managers of the same sector through association.

7.  Report to Bureau of Energy Efficiency (BEE) and state level designated agency about the action taken on the recommendations of accredited energy auditor in the prescribed format.

8.    Establish good system of data recording and to analyze the energy consumption trends.

Future Aspects:

It is more likely that Energy Managers will become progressively involved in the conceptual and design stages of projects so as to reflect on the impact made by the design and operation of new generation of process and service industry.        

Automatic Power Factor Controller for Industries

Induction motor accounts for more than half of the industrial load and are responsible for the poor power factor. The power factor of an induction motor varies with the load on the motor. Lightly loaded motor has a very poor power factor. Poor power factor results in reduced capacity of transformers, cables and other equipments and are also responsible for higher power losses because of increased current flow. They also cause additional voltage drop.

Motivation for power factor improvement:  

Utilities usually encourage the consumers to improve the power factor of their installation by incorporating power factor based penalty/rebate in the power tariff structure.

Figure shows the Electricity Bill of a Hotel for the month of Dec 2016. The premises, which is fed from 11 kV, is having an average power factor of 0.63 (as can be seen in the picture) for which the consumer has to pay a penalty of 28,759 INR ( a hefty amount indeed, for sheer casual approach)

Coal-fired Power Plants: Hazardous to your Health

The aspiration for rapid economic growth leading to express industrialization, accelerated urbanization and mechanization of agriculture has been responsible for the increasing energy demand ever since the independence in India. In the recently concluded 21^st Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC) in Paris, a resolution on limiting the use of coal across countries was proposed for consideration. Coal-fired power plants are among the most polluting industrial facilities. This is of particular relevance in the Indian context as coal fired power plants form the back bone of Indian electricity generation sector.

Pollution from Coal-fired Power Plants

In 2014, nearly 79% of the electricity generated in India was from thermal power plants. Power plants in the country use different qualities of coal, different combustion technologies and operating conditions. As a result these plants have different efficiencies and different emission levels. Main emission from lignite based coal-fired  power plants are CO₂, NOx, SOx and air borne particles such as fly ash, soot, Suspended Particulate Matter (SPM) and other trace gases. 

As per the Central Electricity Authority (CEA) report the best specific coal usage for any Indian coal-fired power plant is less than 0.6 kg/kWh whereas the worst has been 1.0 kg/kWh. The Indian coal has high ash content (35-50%) and low Calorific Value (CV), about 2500-5000 kCal/kg. Low CV means more coal usage and high ash disposal requirements. 

The emissions per unit of electricity generated (kWh)  are estimated to be in the range of 0.91 to 0.9 kg/kWh for CO₂, 6.94 to 7.2 g/kWh for SO₂ and 4.22 to 4.38 g/kWh for NO during the year 2010. The future emission scenario (for the year 2020-21), based on the projected coal consumption in Indian coal-fired power plants is in the range of 714976 to 914680 Gg of CO₂, 4734 to 6051 Gg SO₂ and 366 to 469 Gg of NO. The continued use of older coal-fired power plants, many of which have minimal or no pollution controls and the construction of more of these power plants will only worsen the situation.

Health Hazards from Coal-fired Power Plants

So these coal-fired power plants, by burning of coal, releases a lot of Green House Gases (GHG) and other harmful pollutants into the atmosphere. These pollutants such as Sulphur-dioxide, Nitrogen Oxides and particulate matters released in the air and water, may cause respiratory problems along with other serious health consequences. Pollution produced by these plants is responsible for thousands of non-fatal heart attacks and millions of Asthma attacks each year.

Coal-fired power plants annually produce millions of tons of Coal Combustion Waste (CCW) – coal ash, scrubber sludge and other by-products. This waste contains toxics such as arsenic and heavy metals. Arsenic increases the risk of skin, lung, bladder, liver, kidney and prostate cancer. It can also cause liver disease, anaemia, gangrene and various skin diseases. Heavy metals such as cadmium, chromium, lead, mercury, nickel etc. can cause cancer, nervous system and brain damage and learning and behavioural problems in children.

A single large power plant may require several hundred acres of landfill space to dispose of its coal ash causing damage to the green land. The pollutants in the coal ash can get into the soil and contaminate the nearby ground water and make the drinking water hazardous.

Pollution from NTPC's Badarpur Coal-fired Power Plant: An example

Barely 25 km from the Central Delhi, a 40 year old coal-fired power plant run by NTPC is working way beyond its life. Along with other reasons this power plant is responsible in listing Delhi, the Indian capital, as one of the worst air polluted cities in the world. It is ranked at 11th position among the most polluted cities on the Earth with worst air quality, a WHO report says.  

New Delhi has the world's highest levels of tiny, toxic particles that lead to respiratory diseases, lung cancer and heart attacks as already mentioned above. The city averaged 153 micrograms/cubic meter in the year 2013 as per the WHO report. The level of pollution reported is 15 times higher than the WHO's recommended pollution level. PM 2.5 level has been increasing in the city since last 5 years and the measured average annual PM 2.5 was 122, whereas WHO recommends that it should be kept below 10.  Residents nearby the power plant go out using handkerchiefs as masks to avoid breathing soot and fly ash. Eye burns and headaches because of coal dust are common to many residents.

National Thermal Power Corporation (NTPC) is now seeking to cut emissions across its facilities in the country and is planning to spend 12 billion INR annually on technology upgrading to enhance efficiency and reduce the pollution.      

Future Agenda

Now the question is who is responsible for all this, the government, the utilities, the pollution controlling agencies or somebody else. Can we play a more interactive role in reducing the deadly pollution? The answer is YES. To meet the future energy needs safely while protecting Human health and the nature, we must:

1.        Judiciously use the energy with greater efficiency i.e. increase energy efficiency and conservation, and
2.          Aggressively pursue RE resources such as Solar, Wind, Bio-mass etc.
3.        We must eliminate these polluting power plants in phases like France.

Get ready for the Net Metered Solar PV System

Rapidly depleting fossil fuel reserves, higher energy demands, ever increasing global pollution- the present scenario has made it essential for us to look for other sources of energy. Solar PV energy has emerged as a convenient, pollution free and mature solution to this problem.

In India, the solar PV system has generated much curiosity among the common people about its use, the subsidies granted by various government agencies, the business opportunities in solar industry etc. It has created an atmosphere of awareness among the masses. It will promote de-centralized electricity generation thereby reducing the transmission and distribution losses, which is significantly high in the country.   

The state of Madhya Pradesh is bestowed with high solar radiation (5.5 kWh/m²/day on an average) and around 300 days of clear sunny day per annum. The state has a proposed Solar PV capacity addition target of 2200 MWp by 2022. The Madhya Pradesh Solar Policy 2012 has given the much needed thrust for installation of grid connected Solar PV projects. 

The most recent and much talked about development that has caught the attention of the people is the Net-metering. The state policy for ‘Net metering based solar applications: 2015’ has been structured so as to promote generation and self consumption of energy generated from solar PV system by individuals. Now let us see what the net metered solar PV system is all about.

What is Net-Metering or Net-metered solar PV system?

In the grid connected system, the solar PV system is installed at the roof top or within the premises of the consumer (existing electrical energy user). The power produced by solar PV system will be used by the consumers for their own use. The energy produced in excess of the consumer’s requirement could be injected into the utility’s LT network. In case the energy need of the building is more than that generated by the solar PV system, then the required additional energy will be drawn from the LT lines.

A bi-directional or import-export energy meter has to be installed for keeping the energy record. The electrical energy thus exported could be adjusted against the import by the consumer from the utility network. Such type of solar PV system is known as ‘Net metered Solar PV system’. The consumer, after settlement of energy within the settlement period, shall pay for the net energy purchased by him/her from the utility.

The concept seems to be good, but the question arises is who can install the net metered solar PV system?  

Who can apply for Net-metered solar PV system (Eligibility Criteria)?

All categories of electrical consumers who have installed solar PV system in their premises, or are willing to install, to balance part or all of their electrical energy needs are eligible for ‘net metering’ Solar PV scheme. The solar PV system can be either self owned or third party owned.  

Every activity or installation in which any government organization is involved, has its own set of sanction procedures. Now the question is, where the interested party can apply and what are the approval procedure? 

     

What is the Approval Procedure?

The eligible consumer is required to fill and submit an on-line application form along with the necessary fee and documents such as current electricity bill. The form is available at the MP Urja Vikas Nigam (MPUVN) and the Distribution Companies (DISCOM) website.

Once the solar PV beneficiary (a person who is willing to install the solar PV system at his/ her own premises) applies for "Net metered" solar PV system at his premises along with the registration fee of 1000 INR (as on May 2017), the Discom official shall visit the said premises for verifying the technical feasibility for grid connection of the proposed Solar PV system. They will inspect the available LT network, in case the application is for residential use. The available capacity of the concerned distribution transformer should also be ascertained before giving the sanction. The applications are to be handled on first come first serve basis. As per current rules, the total capacity of grid tie solar PV system on any distribution transformer cannot exceed 30% of the transformer's kVA capacity. The approval procedure is supposed to take nearly 30 days from the date of application.

The eligible consumers have to complete the installation of the approved Solar PV system within 3 months from the date of approval by DISCOM, otherwise the sanction will be cancelled.

This solar PV system is supposed to feed back the extra energy produced to the grid, means you are connecting your solar PV to the utility grid. For this you certainly have to follow a set of safety and technical rules and regulations. What are these rules and regulations?  

What are the safety and technical points of the system?

The Solar PV system is expected to have a lifespan of 25 years. Also the system is to be grid tied; hence utmost care should be taken during the installation process so as to ensure that every safety and technical standards are followed. 

The interconnection with the LT network shall be made as per the technical standards for “connectivity of distributed generation resources regulations” notified by Central Regulatory Authority (CEA). Similarly, metering arrangements should confirm to MP Electricity Regulatory Commission (MPERC) “Grid connected Net metering Regulations 2014” and subsequent amendments thereof and CEA Regulation 2006 for the “Installation and Operation of meters”.   

One of the most important and typical safety requirement of Net- metered or Grid-Tie solar PV system is the "anti-islanding" feature. In this feature it is mandatory that the grid-tie solar system must be shut down automatically in case of grid failure so as to ensure that the associated utility network and equipments are safe to work on. This safety feature is essentially incorporated in the grid-tie inverter. 

MPUVN ltd., New and Renewable Energy department, Government of Madhya Pradesh, shall be the nodal agency for Net-metering based Solar PV systems in the state. To ensure quality work the consumer has to get the installation work done by developers/facilitators empanelled with the MPUVN.

Is there any tax benefit or financial assistance for the system?

Installation of Solar PV systems under the policy shall be exempted from wheeling, cross-subsidy and open access charges. The energy generated from the solar PV system shall be exempted from electricity duty and cess. All eligible consumers can avail the financial assistance from Ministry of New and Renewable Energy (MNRE) as per the applicable schemes. The equipments for the solar PV system under this policy shall be exempted from VAT and entry tax.    
      

Even after the steep growth in this sector if you have not installed a roof top solar PV system at your house, it is high time now to awaken from your slumber and acknowledge the technology; at least for the sake of your future generation.