:

  Load Type/Capacity

  Inverter/UPS Size & Type

  Backup Time

  Grid Supply (Utility)/Generator Availability

  Battery Type

  Budget

LOAD TYPE / CAPACITY

In a bid to design an effective and functional Solar, Inverter, or UPS system, it is pertinent to understand the type of load to be powered. This is so important to determine the Size and Type of UPS/Inverter that would be capable of handling such loads.

We have different types of load and these loads play a huge part in the effective functionality of the UPS/Inverter system. The Load Types Include Basic Loads (Household & Office appliances); Inductive Loads (Elevators, Escalators, Medical Equipment, etc.) as well as Very Sensitive/Critical Loads (IT Equipment, Medicals, etc.).

The Cumulative of these load wattages determines Size and Type of UPS / Inverter be used.

INVERTER/UPS SIZE & TYPE

What is an Inverter?

An inverter is a compact, rectangular-shaped piece of equipment that is usually powered by either a combination of batteries hooked together in parallel or by a single 12V or 24V battery. In turn, these batteries can be charged by PHCN supply, gas generators, automobile engines, solar panels, or any other conventional sources of power supply.

The primary function of an inverter is to convert Direct Current (DC) power into standard, Alternating Current (AC). This is because, whereas AC is the power supplied to industry and homes by the main power grid or public utility, the batteries of alternating power systems store only DC power. Moreover, virtually all household appliances and other electrical components and equipment depend solely on AC power to perform.

UPS Vs. Inverter

• The basic function of both Inverter and UPS is the same in that they store electricity in a battery when power is available, and provide it to various devices in the event of an electricity outage. However, they both are different in their circuitry, price, functions, etc. All UPS contain an inverter as well as a battery charger, but not all inverters offer a built-in battery charger, which would then need to be purchased separately.

• A key difference between an inverter and a UPS is the time taken by them to provide power supply from the batteries in the event of a power failure: an off-line UPS (the standard) switches to battery power within 3 to 10 ms after mains power has been lost. An inverter changes over in anything from 25 to 500 milliseconds. Gadgets that can’t tolerate even this time lag or which may be damaged by being incorrectly shut down, such as a computer or sensitive medical equipment, are paired up with a UPS rather than an inverter, precisely for this reason.

• Another notable difference between the two, is that true online double-conversion UPS are credited with regulating and monitoring the fluctuations in the flow of electricity. UPS protect against line abnormalities like surges, voltage fluctuation, under-voltage, over-voltage, spikes, and noise. This is the main reason why electronic devices featuring delicate circuitry are backed-up using a UPS, instead of an inverter. The same doesn’t hold for

the inverter, as it simply stores and relays electricity in the event of a power failure, but it doesn’t monitor it.

Types of Inverter Based on Output Waveform

True Sine Wave Inverters have been developed to replicate, if not improve, the quality of power provided by main power grids or power utilities. They are specifically recommended to power high energy-consuming electronic gadgets and equipment. True Sine Wave inverters are more expensive than Modified Sine Wave inverters and are the more powerful and efficient option of the two.

Modified Sine Wave inverters are much cheaper and are capable of running fewer or selected number of household appliances and fixtures, for example – kitchen appliances, lights, and small power tools. However, this type of inverter may not possess the capacity to power high energy-consuming equipment and appliances, for example – computers, microwave ovens, air-conditioners, heaters, and laser printers.

Square Wave Inverters are the simplest form of output wave available in the cheapest form of inverters. They can run simple appliances without problems but not much else, it would damage such appliance(s).

 Based on Size & Battery Configuration

The size of inverters ranges from as low as 100w, to well over 5000w. This rating is an indication of the capacity that the inverter can simultaneously and continuously power a high-wattage piece of equipment or appliance or a combination of multiple units of such items.

The Battery Voltage also ranges from 12VDC to as high as 720VDC

BACKUP TIME / AUTONOMY

This is the estimated period for the specified load to run on the battery (accumulator) when there’s a power outage. The backup time determines the number of batteries that would be sufficient to cater for the specified load within the specified time ceteris paribus.

It should, however, be noted that if the load is increased beyond the specified load level, the backup time decreases and vice-versa.

SUPPLY FROM GRID

The Grid is critical to the effective running of the inverter/UPS/Solar Solution.

The Inverter/UPS systems rely solely on the grid to charge the batteries for storage in the event of a power outage.

The requirement of the Grid is OPTIONAL when designing for Solar solution depending on clients’

specification: OFFGRID or HYBRID

INVERTER BATTERY & TYPES

Inverter batteries are designed to better handle the power requirements of a power backup supply system. It is quite different from car batteries because, under normal operation, inverters require a large amount of current to supply to appliances/devices over a long period.

Hence, the Inverter battery must be able to supply a reasonable amount of current over long periods whereas car battery is designed for mainly starting the car engine and maybe power the car electronics, which are mostly low power.

All inverter batteries in the market are rechargeable lead-acid batteries. Some require more maintenance, and some are ‘almost’ maintenance-free. They are usually rated 2V, 6V, and 12V. Broadly speaking, there are two ways to categorize lead-acid inverter batteries.

When differentiating batteries based on electrolyte technology, the two battery types are:

• Flooded or Wet Cell batteries or VLA battery

• Sealed Lead Acid (SLA) or Gel Cell batteries or VRLA battery

Flooded or wet cell batteries are the standard lead-acid batteries which require more maintenance and need to be kept upright all the time. SLA batteries are also known as maintenance-free batteries, although it still requires some sort of cleaning and is more expensive than flooded ones.

When differentiating batteries based on plate technology, the two battery types are:

• Flat Plate

• Tubular inverter batteries

Tubular inverter batteries are more sophisticated with a life span that could be 8- 10 years and are more efficient than flat plate lead-acid batteries.

Note: You’ll find wet cell battery with a flat and tubular plate and similarly you’ll get gel cell battery with flat and tubular plates.

COMMON TERMS USED IN SYSTEM DESIGN

• Watt (W): Watt is the measure of how much power a device uses when turned on or can supply.

If a device uses 100 watts, it is simply the voltage times the ampere (rate of current). If the device takes 10 Amps at 12 Volt DC, it uses 120 watts power. That is 10A x 12 V = 120 W.

• Watt Hour (WH): A watt-hour (or Kilo Watt-hour – kWh) is simply how many watt times, how many hours the device is used. If the device uses 100 watts for 10 hours, it is a 1000-watt hour or

1 kWh. The electricity tariff is based on kWh.

• Ampere (A): It is the measure of electrical current at the moment. Amps are important to determine the wire size for connecting the inverter to the battery. Low gauge wire will heat up and burn if heavy current flows through it from the battery.

• Ampere Hour (Ah): Amp-Hour usually abbreviated as Ah is the Amps x Time. Ah is the measure of battery capacity which determines the backup time of the inverter

SOLAR ENERGY

Solar energy is created from sun radiation.

Solar power is captured when energy from the sun is converted into electricity or used to heat air, water, or other fluids.

There are currently two main types of solar energy technologies:

• Solar thermal: these systems convert sunlight into thermal energy (heat). Most solar thermal systems use solar energy for space heating or to heat water (such as in a solar hot water system). However, this heat energy can be used to drive a refrigeration cycle to provide for solar-based cooling. The heat can also be used to make steam, which can then be used to generate electricity using steam turbines. It is considered more efficient to build solar thermal electricity generators at large scale, typically in the tens to hundreds of megawatts

• Solar photovoltaic (PV): the conversion of sunlight directly into electricity using photovoltaic cells. PV systems can be installed on rooftops, integrated into building designs and vehicles, or scaled up to megawatt-scale power plants.

one form to another. For example, with the help of a heat engine, the conversion process takes place in a dam, where potential energy is converted to kinetic energy using the turbine in flowing water, then the kinetic energy is finally converted to electricity through an electric generator. This illustration shows how the heat engine as a device converts one form of energy to another.

Mathematically, the energy conversion of a device is given as:

 Device efficiency = Useful energy output / Energy input

 According to the 1^st law of thermodynamics, energy is conserved in all its transformations.  The useful energy speaks about the purpose of the device. Another example of a device is the electric heater which gives its energy output as heat and the energy input is the electricity.

Other examples of tasks performed by common energy conversion devices (Table 1.1)

 Energy conversion devices& their efficiencies (Table 1.2)

Table 1.2 above explains how efficiency is quantified and how some energy conversion devices are more efficient than others. It should be noted that higher efficiency means lower energy costs.

Implementation Measures:

 Energy Production

There is a need to introduce more efficient generation/conversion through:

• Waste reduction from electricity generation
• Improved maintenance practices
• Utilization of energy-saving and efficient technologies for power generation e.g. solar systems
• Application of modern process technologies like clean coal processes.

Energy transmission and distribution of electricity:

 The mode of transmission and distribution of energy from the point of generation to the end-users should be done efficiently with improved control of systems, e.g. better balancing of phases, voltage regulation, power factor improvement,

• Efficient and increased distribution of power
• Higher transmission voltages
• State-of-the-art technologies such as low-loss transformers, smart metering, etc.

Energy Consumptions

Acquisition of energy-efficient equipment e.g. refrigerators, boilers, furnaces, industrial dryers, pumps, compressors, lighting, domestic appliances, air conditioning systems. This is highly essential in areas where equipment is operated over long periods.

Improved maintenance of all equipment.

Improved metering of fuel, electricity, and stream flows. Also, Information on energy usage allows consumers to appreciate better the quantities of energy consumed and the time and purpose of such consumption: this is also an important step to improving energy efficiency,

Need for Behavioral Change:

Monitoring energy efficiencies of equipment to ensure design operating parameters and performance is perfect.

 Changes in equipment usage both at home and in the office, such as switching off appliances that are not needed and avoiding excessive use of “phantom energy” for many types of equipment.

Choosing efficient modes of transportation e.g. public transport versus cars for individuals, rail versus road for freight, where such alternatives are available

Benefits of Energy Efficiency Implementation

Energy Efficiency Implementation is highly beneficial for all energy consumers,

• It reduces operational cost
• It improves the quality of life
• It reduces carbon footprint
• It increases revenue for consumers when they invest in clean technologies over those who are not.
• It can also be beneficial for various business sectors that consume a large amount of energy like schools, factories, malls, financial institutions, etc.

More importantly, when energy efficiency measures are implemented at homes or in businesses, it results in high behavioral changes. The benefits of these changes propel the consumer to keep doing more to increase their savings. These behavioral changes like turning off lights when not in use, installing thermostats, and regular maintenance of equipment, create more awareness for others to become more energy efficient.

Energy Efficiency Programs that can aid the process of implementation.

• Development of energy efficiency policies and strategies.
• Energy awareness in line with consumption and related aspects of energy efficiency.
• Encouraging energy auditing and energy assessment both in the public and private sectors.
• Publicity and development of energy efficiency best practices, and information on norms and standards applicable to different sectors.
• Promotion and facilitation of international collaboration and cooperation.

In conclusion

Implementing energy-efficient measures at all stages of energy generation and utilization could reduce significantly the negative impacts of energy use on the environment and human well-being, and proliferate the availability of primary energy reserves while achieving maximum benefits in terms of outputs from the available energy. This will reduce the cost to both producers and users, as well as maintain the same level of energy-dependent activities.