Small household cost of the system
An Introduction
Since the 1980s, along with the development and utilization of solar energy photovoltaic industry has become the world's growth
than the fastest high-tech industries - the continuous improvement of the importance of renewable energy and solar cell conversion
efficiency, with the countries of the world The PV industry is growing at rapid speed of rapid development, especially for those
who live in scattered and inaccessible, it is difficult to solve the problem of electricity through an extension of the public
power grid of regions, solar power system a huge potential market.
However, in some small users in the design of photovoltaic power generation system, often there are some problems: such as the
design of capacity in order to meet the requirements of low cost, is obviously insufficient; the blind pursuit of high reliability,
the request can not be power outages, greatly increasing the investment costs. The battery capacity is too large, not only
increased investment, resulting in a waste, but also easy to form the charge is insufficient. Based on the small household
photovoltaic system design, and affect its cost of power generation systems a major factor analysis, to meet the load coverage, to
ensure the optimization of the system and economy.
Two photovoltaic system cost analysis
Photovoltaic power generation system life cycle cost C is:
C = Cs W + Cbb (1)
: Cs PV module unit price ($ / kWh); W is the solar peak wattage; Cb is the unit price of the battery; b is the capacity of the
battery.
Constraint function of the system are as follows:
LOLH (w, b) = TK (2)
: TK loss of power for the users allowed to count the hours Mi: LOLH (w, b) in case of loss of power the number of hours of TK,
the relationship between the solar peak wattage Wc and battery capacity b.
Can be seen from the above equation, the cost of photovoltaic systems and photovoltaic components and the battery capacity has
a linear relationship, and subject to the constraints of the number of hours of lost power.
Three cost impact factor analysis
A battery's capacity
Continuous rainy days and load allowed maximum number of hours of lost power during the battery capacity design through to the
largest considered photovoltaic system installation site to determine the battery of self-sufficiency. In addition, the battery
capacity and battery discharge rate and ambient temperature.
(1) of the battery discharge rate capacity
A corresponding increase in the capacity of the battery with the lower discharge rate.
Where: S is the average battery discharge rate (h): D for self-sufficiency in the number of days, Pi is the load power (w); Ti
load working hours (h); the DOD is the maximum depth of discharge of the battery.
Capacity correction factor can be detected by the battery discharge rate and temperature.
(2) ambient temperature battery
The capacity of the battery:
Where: Ld, 1 for one days accumulated and load power consumption (kwh); D is the self-sufficiency in the number of days, L is
the decay rate; N the number of the battery; Vb is the nominal battery voltage (V), lead-acid batteries occasions 2Vt battery
voltage by the discharge rate of the volume correction factor.
When the battery temperature drops, the battery capacity will decrease. The trend shown in Figure 3.
Affected by temperature, the maximum depth of discharge of the battery as follows:
DODb = DODx [1 ten a (t-25)] (5)
: A battery temperature coefficient (1 / ° C).
The capacity of the battery can be amended to read:
Capacity of PV modules
Solar module capacity formula:
Where: EL is a year in the load power consumption (electricity required) (kwh / year); of Pas as under standard conditions
(AM1.5, sunshine intensity 1000W/m2, solar cell temperature of 25 ° C) of the sun the output of the cell array (A ? h); 2 is the
output efficiency of PV modules; T is the peak hours of solar modules.
Estimates of the peak hours of solar modules for T = I
Calculation and analysis of the four instance
Sonid Right Banner of Inner (latitude 42 degrees 28 minutes east longitude 112 degrees 57 minutes), a photovoltaic home
systems, for example, the daily electricity consumption of about 2.0 degrees, the loss of power the number of hours allowed in one
year 8 hours, the load coverage of 98%. Meteorological data of the solar energy resources in the ground effect, according to Table
1.
Based on the table, you can calculate the annual average radiation total of the Suniteyou flag horizontal 1.59MWh/m2/yr. The
installed inclination to adopt the method of the year, adjusted twice, 4-9 months for 30 degrees, 60 degrees in other months. The
available tilted PV modules installed on the annual total average radiation 2.0MWh/m2/yr. ±: in the month of December the average
daily irradiation, the PV system design, in order based on computer simulation of the PV module technology battery capacity based
sauce.
This example, the selection of deep discharge lead-acid batteries, depth of discharge at 25 ° C to 80%. No sunshine time and
the average monthly minimum temperature, preferable battery of self-sufficiency in the number of days for six days, from (3) can be
drawn from the discharge hour rate of 59.5 hours battery capacity from Figure 2 investigation was hours amendment 70% by the
formula (5) depth of discharge was 61%. The battery's rated capacity for 200A.h coulombic efficiency of 86%. From Figure 4, the
initial cost and total cost of the power generation system increases with the increase of the battery capacity, battery increase
6@200A.h the total cost increase of 3%. The depth of discharge of the battery decreases with the increase of the capacity. When the
battery capacity is 72@200A.h, its depth of discharge, after 6 days without sunshine is about 60% less than the battery allows 61%
depth of discharge, the battery will not discharge. Battery calculated by the formula (6) the capacity 72@200A.h, consistent with
Figure 4.
It can be seen from Figure 5, rise with the increasing power of PV modules, the total system cost and power generation. PV
module power increase per 0.lkW total cost increase of about 3.7 percent, generating about 72%.
Figure 6 shows the same user electricity load conditions, with the average monthly increase of radiation exposure, the capacity
of the PV modules decreased total generating costs decline. The month the average daily irradiation reached or exceed 3.8kW/m2/d
when the capacity of PV modules required to achieve the minimum 0.9kW, the cost of power generation to meet the minimum.
The loss of power hour TK different decisions on coverage of the different load. Figure 7 for the system at different load
coverage, loss of power hour TK between PV modules and batteries variation. With the rise in coverage of the load (power failure
hours decrease) increase the capacity of PV modules and batteries. Figure 7 shows the monthly average radiation exposure of the
lowest in December, to ensure the system load of 98% coverage (loss of power hours / year) 8h battery for 72@200A.h PV modules The
capacity of 2.0kW. The juice of this value by equation (7) count derived from the PV module capacity 1.9kW similar.
Five summary
A small household photovoltaic power generation system not only low cost but also to load coverage, that is, loss of power
hour. Small household photovoltaic systems, photovoltaic modules for each additional O.1kw, power generation system cost increase
of about 37% battery capacity each increase 1200A.h of, the total cost increase of about 3%. Therefore, according to the location
of the solar photovoltaic system installation resources (such as the sun monthly average radiation exposure, no duration of
sunshine, year, the lowest temperature, and the user to allow the largest loss of the number of hours) reasonable to select the PV
modules and batteries the capacity to achieve the lowest cost of power generation systems, and to ensure the optimization of system
operation.
