- Features of solar energy in mid-latitudes
- Economic feasibility
- The main types of solar panels
- Solar energy complex equipment
- Household application
Alternative energy is becoming more affordable. This article will give you a complete understanding of local-scale solar energy, types of solar cells and panels, principles of building solar farms and economic feasibility..
Features of solar energy in mid-latitudes
Alternative energy is very attractive for residents of middle latitudes. Even in northern latitudes, the average annual daily radiation dose is 2.3–2.6 kWh / m2. The closer to the south, the higher this indicator. In Yakutsk, for example, the intensity of solar radiation is 2.96, and in Khabarovsk – 3.69 kWh / m2. Indicators in December range from 7% to 20% of the average annual value, and in June and July they double.
Here is an example of calculating the efficiency of solar panels for Arkhangelsk, a region with one of the lowest indicators of solar radiation intensity:
- Q is the average annual amount of solar radiation in the region (2.29 kWh / m2);
- TOoff – coefficient of deviation of the collector surface from the southern direction (average value: 1.05);
- Pnom – the rated power of the solar panel;
- TOsweat – loss coefficient in electrical installations (0.85–0.98);
- Qisp – the radiation intensity at which the panel was tested (usually 1000 kWh / m22).
The last three parameters are indicated in the passport of the panels. Thus, if KVAZAR panels with a nominal power of 0.245 kW operate in the conditions of Arkhangelsk, and the losses in the electrical installation do not exceed 7%, then one block of photovoltaic cells will provide generation of about 550 Wh. Accordingly, for an object with a nominal consumption of 10 kWh, about 20 panels will be needed..
The payback periods for solar panels are easy to calculate. Multiply the daily amount of energy produced per day by the number of days per year and by the service life of the panels without derating – 30 years. The electrical installation considered above is capable of generating an average of 52 to 100 kWh per day, depending on the length of daylight hours. The average value is about 64 kWh. Thus, in 30 years, the power plant, in theory, should generate 700 thousand kWh. With a one-part rate of 3.87 rubles. and the cost of one panel is about 15,000 rubles, the costs will pay off in 4–5 years. But reality is more prosaic.
The fact is that the December values of solar radiation are less than the average annual by about an order of magnitude. Therefore, fully autonomous operation of the power plant in winter requires 7-8 times more panels than in summer. This significantly increases the investment, but reduces the payback period. The prospect of introducing a “green tariff” looks quite encouraging, but even today it is possible to conclude an agreement for the supply of electricity to the grid at a wholesale price that is three times lower than the retail tariff. And even this is enough to profitably sell 7-8 times the surplus of generated electricity in the summer.
The main types of solar panels
There are two main types of solar panels.
Solid silicon solar cells are considered first generation cells and are the most common: about 3/4 of the market. There are two types of them:
- monocrystalline (black) have a high efficiency (0.2-0.24) and a low price;
- polycrystalline (dark blue) is cheaper to manufacture, but less efficient (0.12-0.18), although their efficiency decreases less with diffused light.
Soft photocells are called film cells and are made either from silicon spraying or by a multilayer composition. Silicon cells are cheaper to manufacture, but their efficiency is 2–3 times lower than crystalline ones. However, in diffused light (twilight, overcast) they are more effective than crystal.
Some types of composite films have an efficiency of about 0.2 and cost much more than solid elements. Their use in solar power plants is highly questionable: film panels are more susceptible to degradation over time. Their main area of application is mobile power plants with low energy consumption.
Hybrid panels include, in addition to the photocell unit, a collector – a system of capillary tubes for heating water. Their advantage is not only in saving space and the possibility of hot water supply. Due to water cooling, solar cells lose less performance when heated.
Table. Manufacturers overview
Model SSI Solar LS-235 SOLBAT MCK-150 Canadian Solar CS5A-210M Chinaland CHN300-72P Country Switzerland Russia Canada China A type Polycrystal Monocrystal Monocrystal Polycrystal Power at 1000 kWh / m2, W 235 150 210 300 Number of elements 60 72 72 72 Voltage: no-load / under load, V 36.9 / 29.8 18/12 45.5 / 37.9 36.7 / 43.6 Current: under load / short circuit, A 7.88 / 8.4 8.33 / 8.58 5.54 / 5.92 8.17 / 8.71 Weight, kg nineteen 12 15.3 24 Dimensions, mm 1650x1010x42 667x1467x38 1595x801x40 1950x990x45 Price, rub. 13,900 10,000 14,500 18150
Solar energy complex equipment
The batteries generate up to 40 V direct current during operation. To use it for domestic purposes, a number of transformations are required. The following equipment is responsible for this:
- Battery pack. Allows you to use the generated energy at night and at low intensity hours. Helium batteries with a nominal voltage of 12, 24 or 48 V are used.
- Charge controllers maintain optimal battery life and transfer the required power to consumers. The necessary equipment is selected for the parameters of batteries and accumulators.
- The voltage inverter converts DC to AC and has a number of additional functions. Firstly, the inverter sets the priority of the voltage source, and if there is a lack of power, it “mixes” the power from another. Hybrid inverters also allow the surplus of generated energy to be transferred to the city grid.
1 – solar panels 12 V; 2 – solar panels 24 V; 3 – charge controller; 4 – battery 12 V; 5 – 12V lighting; 6 – inverter; 7 – “smart home” automation; 8 – battery block 24 V; 9 – emergency generator; 10 – main consumers of 220 V
Solar panels can be used for absolutely any purpose: from compensating for the received energy and supplying individual lines to complete autonomy of the power system, including heating and hot water supply. In the latter case, an important role is played by the large-scale application of energy-saving technologies – recuperators and heat pumps..
In mixed use, solar energy uses inverters. In this case, power can be directed either to the operation of individual lines or systems, or to partially compensate for the use of city electricity. A classic example of an efficient power system is a heat pump powered by a small solar power plant with a battery bank.
1 – city network 220 V; 2 – solar panels 12 V; 3 – 12V lighting; 4 – inverter; 5 – charge controller; 6 – main consumers of 220 V; 7 – battery
Traditionally, panels are installed on the roofs of buildings, and in some architectural solutions they completely replace the roof covering. In this case, the panels must be oriented to the south side in such a way that the incidence of rays on the plane is perpendicular.