Solar System Devices & Equipments

Solar Panel refers to a panel designed to absorb the sun’s rays as a source of energy for generating electricity. A photovoltaic (PV) module is a packaged, connect assembly of typically 6×10 photovoltaic solar cells. Photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies solar electricity in commercial and residential applications. Each module is rated by its DC output power under standard test conditions (STC), and typically ranges from 100 to 365 watts. The efficiency of a module determines the area of a module given the same rated output – an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. There are a few commercially available solar modules that exceed 22% efficiency and reportedly also exceeding 24%.A single solar module can produce only a limited amount of power; most installations contain multiple modules. A photovoltaic system typically includes an array of photovoltaic modules, an inverter a battery pack for storage, interconnection wiring, and optionally a solar tracking mechanism.

Maximum Power Point Tracking (MPPT Controller ) is a technique used commonly with wind turbines and photovoltaic (PV) solar systems to maximize power extraction under all conditions. Although solar power is mainly covered, the principle applies generally to sources with variable power: for example, optical power transmission and thermo photovoltaics. PV solar systems exist in many different configurations with regard to their relationship to inverter systems, external grids, battery banks, or other electrical loads. Regardless of the ultimate destination of the solar power, though, the central problem addressed by MPPT is that the efficiency of power transfer from the solar cell depends on both the amount of sunlight falling on the solar panels and the electrical characteristics of the load. As the amount of sunlight varies, the load characteristic that gives the highest power transfer efficiency changes, so that the efficiency of the system is optimized when the load characteristic changes to keep the power transfer at highest efficiency. This load characteristic is called the maximum power point and MPPT is the process of finding this point and keeping the load characteristic there. Electrical circuits can be designed to present arbitrary loads to the photovoltaic cells and then convert the voltage, current, or frequency to suit other devices or systems, and MPPT solves the problem of choosing the best load to be presented to the cells in order to get the most usable power out.

Charger – The charging protocol (how much voltage or current for how long, and what to do when charging is complete, …, for instance) depends on the size and type of the battery being charged. Some battery types have high tolerance for overcharging (i.e., continued charging after the battery has been fully charged) and can be recharged by connection to a constant voltage source or a constant current source, depending on battery type. Simple chargers of this type must be manually disconnected at the end of the charge cycle, and some battery types absolutely require, or may use a timer to cut off charging current at some fixed time, approximately when charging is complete. Other battery types cannot withstand over-charging, being damaged (reduced capacity, reduced lifetime) or overheating or even exploding. The charger may have temperature or voltage sensing circuits and a microprocessor controller to safely adjust the charging current and voltage, determine the state of charge, and cut off at the end of charge. A trickle charger provides a relatively small amount of current, only enough to counteract self-discharge of a battery that is idle for a long time. Slow battery chargers may take several hours to complete a charge; high-rate chargers may restore most capacity much faster, but high rate chargers can be more than some battery types can tolerate. Such batteries require active monitoring of the battery to protect it from overcharge. Electric vehicles ideally need high-rate chargers; for public access, installation of such chargers and the distribution support for them is an issue in the proposed adoption of electric cars.

Inverter is an electronic device or circuitry that converts direct current (DC) to alternating current (AC).
The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source.
A power inverter can be entirely electronic or may be a combination of mechanical effects (such as a rotary apparatus) and electronic circuitry. Static inverters do not use moving parts in the conversion process.

Deep-cycle battery is a lead-acid battery  or other technologies that designed to be regularly deeply discharged using most of its capacity. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver short, high-current bursts for cranking the engine, thus frequently discharging only a small part of their capacity. While a deep-cycle battery can be used as a starting battery, the lower “cranking current” implies that an oversized battery may be required.
A deep-cycle battery is designed to discharge between 45% and 75% of its capacity, depending on the manufacturer and the construction of the battery. Although these batteries can be cycled down to 20% charge, the best lifespan vs. cost method is to keep the average cycle at about 45% discharge. There is an indirect correlation between the depth of discharge of the battery, and the number of charge and discharge cycles it can perform.

Different Solar Systems

Off-Grid System

An off-grid or standalone photovoltaic system is when your solar photovoltaic system is not connected to the utility grid and you are producing your own electricity via solar, wind, microhydro, generator, etc. These systems will generally have a battery bank in order to store the electricity for use when needed.

These systems allow you to store your solar power in batteries for use when the power grid goes down or if you are not on the grid.  Hybrid systems provide power to offset the grid power whenever the sun is shining and will even send excess power to the grid for credit for later use.

Provides power for your critical loads when the power grid is down.

Sizing the solar array and the batteries required is complex.  Detailed analysis of your requirements will be needed to provide for your minimal critical needs.  You’ll also need to rewire your main electrical panel to isolate the “critical loads” so that only they are provided power in an outage.  This means that your well pump, refrigerator and a few lights are provided power while your air conditioners and TV and other non-essential loads are not.

This is definitely more complex to install as well.  There are dangerous components, mostly dealing with high amp batteries so caution needs to be exercised.  Also, batteries are expensive, require ongoing maintenance and periodic replacement.

Given the additional specialized equipment required and the fact that it requires come complex installation, expect a off-grid system to cost higher to install per watt and to require ongoing maintenance outlays.

Grid-Tie System

A grid-tied electrical system, also called tied to grid or grid tie system, is a semi-autonomous electrical generation or grid energy storage system which links to the mains to feed excess capacity back to the local mains electrical grid. … Conversely when excess electricity is available, it is sent to the mains grid.

Grid-tied, on-grid, utility-interactive, grid intertie and grid back feeding are all terms used to describe the same concept – a solar system that is connected to the utility power grid.
A grid-connection will allow you to save more money with solar panels through better efficiency rates, net metering, plus lower equipment and installation costs: Batteries, and other stand-alone equipment, are required for a fully functional off-grid solar system and add to costs as well as maintenance. Grid-tied solar systems are therefore generally cheaper and simpler to install. Your solar panels will often generate more electricity than what you are capable of consuming. With net metering, homeowners can put this excess electricity onto the utility grid instead of storing it themselves with batteries. Net metering (or feed-in tariff schemes in some countries) play an important role in how solar power is incentivized. Without it, residential solar systems would be much less feasible from a financial point of view. Many utility companies are committed to buying electricity from homeowners at the same rate as they sell it themselves.

Electricity has to be spent in real time. However, it can be temporarily stored as other forms of energy (e.g. chemical energy in batteries). Energy storage typically comes with significant losses. The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates. In other words, more electricity (and more money) goes to waste with conventional battery systems.

Additional perks of being grid-tied include access to backup power from the utility grid (in case your solar system stop generating electricity for one reason or another). At the same time you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.

Grid-Tie System with backup

The Grid-Tie With Battery Backup system can also push excess electricity produced to the electric utility grid but has the added feature of batteries in order to power some selected backup loads when the grid is down. With this benefit comes increased complexity, cost and maintenance requirements.

Without a battery bank or generator backup for your grid inter-tied system, when a blackout occurs, your household will be in the dark, too. To keep some or all of your electric needs (or “loads”) like lights, a refrigerator, a well pump, or computer running even when utility power outages occur, many homeowners choose to install a grid-inter-tied system with battery backup. Incorporating batteries into the system requires more components, is more expensive, and lowers the system’s overall efficiency. However for many homeowners who regularly experience utility outages or have critical electrical loads, having a backup energy source is priceless.

Solar System Applications