Mme solar off grid &on grid solar system -

Topic:Off-grid system&Off-grid system

Two main solar system

Off-grid solar system On-grid solar system

Off-grid PV systems

Standalone photovoltaic power generation system, also known as off-grid PV systems.

In the absence of the grid area, the use of solar modules emit DC, charged by solar battery

charge controller for the use of electrical appliances.

 The DC(direct current) energy of battery can be supplied directly to the DC electrical appliances and other uses, such a system can be called the DC off-grid photovoltaic systems;

  Battery is connected to off-grid inverter, a solar inverter, or PV inverter, converts the variable direct current (DC) output of a photovoltaic (PV) solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid or used by a local, off-grid electrical network. It is a critical component in a photovoltaic system, allowing the use of ordinary commercial appliances. Solar inverters have special functions adapted for use with photovoltaic arrays, including maximum power point tracking and anti-islanding protection.

How off-grid system works

Advantage of off-grid PV systems

Off-grid PV system with its flexible and reliable features meet the demand of grasslands, deserts, islands and other areas home use electricity, and achieved good results.

Small decentralized off-grid PV systems, especially building integrated photovoltaic power generation systems, because of the advantage of small investment ,fast construction, small footprint, policy support ,the off-grid PV systems gradually become the mainstream.

System accessory - solar panels, controller

Solar panels: solar panel is the core part of the solar system, the most valuable part of the whole system . Its role is to conver the sun's radiation to electrical energy stored in batteries or supply for the electrial appliances’work.

Solar Controller: Solar controller's role is to control the working status of the entire system, and protect the battery from discharging or over-discharging. In the large temperature difference condition, the controller should be equiped with temperature compensation function. Its additional features such as light control switch, time control switch ,should be the options of controller.

System accessory - batteries, inverters

Battery: lead-acid batteries, small micro-system, can also use nickel metal hydride batteries, nickel cadmium batteries or lithium batteries. Its role is to store the energy when there is light emitted by the solar panels, and then released when needed.

Inverter: Generally,the direct solar energy output are 12VDC, 24VDC, 48VDC. Providing energy for 220VAC electrical appliance, the DC energy generated by solar power system should be coverted into AC power, so we need to use the DC-AC inverter.

Factors need to consider Off-grid Solar power system design factors to consider are below:

where Solar power system is supposed to install?

How is the solar radiation situation?

The load power of the system ?

What is the system output voltage?DC or AC?

How many hours the system need to work per day?

If there is no sunlight or in rainy weather, the longest days the system needs to continuously supply the power for daily use ?

Load conditions, purely resistive, capacitive or inductive, starting current much?

Case: solar home systems

Generation capacity: 1000 watts

Target facilities: individual residentialUsage: lighting, TV, radio, lights

Advantages: simple structure,Very suitable for living in scattered villages,  

it is more accurate, because the user is a single household

100 ~ 150Wp home solar power system

Load Electric appliance

Type Load powerQuantit

y

Working time per

day

Daily comsuption

Light LED 11W 2 set 3/4 88Wh

Satellite TV Receiver

25W 1set 3/4 100Wh

Color TV 21inch 70W 1set 3/4 280Wh

Total 117W 468Wh

Device configuration:

Solar panel ： 100W~150Wp ；

Maintenance-free batteries ： 50~65AH/24V ；

Inverter ： 150W ； Charge Controller ： 6A ；

Installation: Easy self-installing ★Can work continuously for three rainy days★

Application of off-grid solar system Living in remote areas without electricity, electricity lighting, television, washing

machines and other household electricity; Photovoltaic pump without electricity .deep wells for drinking, irrigation Traffic lights in the field beacon lights, traffic / rail lights, traffic warning / marker

lights, street lights And auto ancillary solar car / electric car, battery charging equipment, car air

conditioners, ventilation fans, refrigerators, etc. Aerospace instrument satellites, spacecraft, space solar power station Communication / Tele communications field solar unattended microwave relay stations,

cable maintenance station, Radio / Communication / Paging power system Petroleum, marine, meteorology oil pipelines and reservoirs gate cathodic protection

solar power systems, oil rigs Health Live and emergency power, marine testing equipment, meteorological / hydrological

observation equipment, etc. Other portable appliances, desalination equipment and power supply

On-grid Pv system

Grid-connected photovoltaic power systems are power systems energized by photovoltaic panels which are connected to the utility grid.

Grid-connected photovoltaic power systems consist of Photovoltaic panels, MPPT, solar inverters, power conditioning units and grid connection equipment.

Unlike Stand-alone photovoltaic power systems these systems seldom have batteries. When conditions are right, the grid-connected PV system supplies the excess power, beyond consumption by the connected load, to the utility grid

How on-grid system works

Feature

Solar energy gathered by photovoltaic solar panels, intended for delivery to a power grid, must be conditioned, or processed for use, by a grid-connected inverter. This inverter sits between the solar array and the grid, draws energy from each, and may be a large stand-alone unit or may be a collection of small inverters, each physically attached to individual solar panels. See AC Module.

The inverter must monitor grid voltage, waveform, and frequency. One reason for monitoring is if the grid is dead or strays too far out of its nominal specifications, the inverter must not pass along any solar energy. An inverter connected to a malfunctioning power line will automatically disconnect in accordance with safety rules,

Another reason for the inverter monitoring the grid is because for normal operation the inverter must synchronize with the grid waveform, and produce a voltage slightly higher than the grid itself, in order for energy to smoothly flow outward from the solar array. For more details on inverter operation

System accessory -DC / AC inverter

DC / AC inverter

The device can Convert the DC power into AC power . Because the current the solar system generate is direct current, and general loads are AC load, the inverter is indispensable.

Grid inverter Is used in the on-grid solar power generation system ,It can feed the

electricity generated by the system into the national grid.

Anti-islanding Islanding refers to the condition in

which a distributed generator continues to power a location even though power from the electric utilityis no longer present. Islanding can be dangerous to utility workers, who may not realize that a circuit is still powered, even though there's no power from the electrical grid. For that reason, distributed generators must detect islanding and immediately stop producing power; this is referred to as anti-islanding.

In the case of a utility blackout in a grid-connected PV system, the solar panels will continue to deliver power as long as the sun is shining. In this case, the supply line becomes an "island" with power surrounded by a "sea" of unpowered lines. For this reason, solar inverters that are designed to supply power to the grid are generally required to have automatic anti-islanding circuitry in them.

Advantages

A grid-connected photovoltaic power system will reduce the power bill as it is possible to sell surplus electricity produced to the local electricity supplier.

Grid-connected PV systems are comparatively easier to install as they do not require a battery system.

Grid interconnection of photovoltaic (PV) power generation systems has the advantage of effective utilization of generated power because there are no storage losses involved.

A photovoltaic power system is carbon negative over its lifespan, as any energy produced over and above that to build the panel initially offsets the need for burning fossil fuels. Even though the sun doesn't always shine, any installation gives a reasonably predictable average reduction in carbon consumption.

Some applications of On-grid system

Photovoltaic power plants: 10KW-50MW independent photovoltaic power plants, scenery (diesel) hybrid power plant, various large parking with charging stations.

solar building will combine solar power and building materials, making the future of large-scale construction to achieve self-sufficiency in electricity is a major future direction of development.

The difference of off-grid and on-grid system 1 Off-grid system can be used in every place,cause it has battery to back up,while on-grid system

should be get connected to national grid;

2Off-grid system is expensive than on-grid one because the battery cost a lot and also the battery have a lifespan for 3-5 years mostly;

3An on-grid system ,the user can sell the additional electricity generated from the system to their country ,this can make profits for users;

4When it is at night,the on-grid system can not supply power,user should trun to the national grid for electricity,but in fact ,if you generate too much energy at day time,you sell to national grid,when you need,you can get from them ,but when it is out of power ,it can not supply energy;

5When it is raining or at night,in a off-grid system,you can use the energy ,because the battery can supply you energy no matter it is our of power of raining ;

Our suggestion for 250kw solar plant system

According to Pakistan’s national grid condition ,our suggestion is choosing off-grid system ,as to 250kw plant ,it is better to choose distributed off-grid system,we can devide the 250kw into three independent part,one is 100kw,another two are 100kw and 50kw or 5 unit 50 kw independent solar system.

Why we can not supple an off-grid system of 250kw plant:

As for as i know in our maket,generally the inverter capacity can reach to 50 kw and the most biggest can be 100kw ,but the stability is said to be not good ;  often for solar plant like 250kw , usually do on-grid system ,but considering Pakistan’s

special condition of national grid,our suggestion is above:Three independent solar system.

Thank you!