314
U. Muntwyler
12.3.7 Off-Grid Installations Without Storage—Solar Pumps
Etc
To eliminate the battery, there are some off grid—application without batteries. These
are DC- or AC-motors for water pumping or for ventilation applications. If a ground
water pumping system is exploited, a water reservoir can act as a cheap and reliable
storage.
12.4 Grid-Connected PV Systems
A grid-connected PV plant consists of three parts:
1. The solar generator (totality of PV modules)
2. A one- or three-phase inverter
3. Some safety devices.
The inverter transforms direct current (DC) from the solar module into alternating
current (AC), as circulating in the local grid (Fig. 12.6).
Grid-connected PV plants come in a whole range of different sizes:
(a) One PV module and one “module or micro-inverter”: 10 W p to 400 W p
(b) String PV inverter systems: 600 W p to 6 kW p for lived-in homes
(c) Multi-String inverter systems: 6 kW p to 120 kW p —residential homes/multistory
houses and commercial buildings
(d) Multiple multi-string PV inverter systems: MW p size—commercial buildings
and power plants.
(e) Central PV inverter systems: 10 kW p to 2 MW p size—commercial buildings
and power plants
(f) Multiple central PV inverter systems: MW p to GW p size—commercial buildings
and power plants
Their electrical diagrams are given in Fig. 12.7a–d [8]:
Due to their simple design, string inverters have obtained, especially in the last
ten years, a higher market share. The central inverters which started 30 years ago,
with 10 kW p units and are now in the MW p size for large utility-scale plants. The
system voltage starts with one PV module with 30 V DC and ranges up to many PV
modules with up to 1500 V DC (Fig. 12.8).
“PV inverters” are inverters, which are designed and built especially for use in
PV systems. During the last 30 years their price has decreased by a factor 10, and
their efficiency has improved from 95% to over 98%.
U. Muntwyler
12.3.7 Off-Grid Installations Without Storage—Solar Pumps
Etc
To eliminate the battery, there are some off grid—application without batteries. These
are DC- or AC-motors for water pumping or for ventilation applications. If a ground
water pumping system is exploited, a water reservoir can act as a cheap and reliable
storage.
12.4 Grid-Connected PV Systems
A grid-connected PV plant consists of three parts:
1. The solar generator (totality of PV modules)
2. A one- or three-phase inverter
3. Some safety devices.
The inverter transforms direct current (DC) from the solar module into alternating
current (AC), as circulating in the local grid (Fig. 12.6).
Grid-connected PV plants come in a whole range of different sizes:
(a) One PV module and one “module or micro-inverter”: 10 W p to 400 W p
(b) String PV inverter systems: 600 W p to 6 kW p for lived-in homes
(c) Multi-String inverter systems: 6 kW p to 120 kW p —residential homes/multistory
houses and commercial buildings
(d) Multiple multi-string PV inverter systems: MW p size—commercial buildings
and power plants.
(e) Central PV inverter systems: 10 kW p to 2 MW p size—commercial buildings
and power plants
(f) Multiple central PV inverter systems: MW p to GW p size—commercial buildings
and power plants
Their electrical diagrams are given in Fig. 12.7a–d [8]:
Due to their simple design, string inverters have obtained, especially in the last
ten years, a higher market share. The central inverters which started 30 years ago,
with 10 kW p units and are now in the MW p size for large utility-scale plants. The
system voltage starts with one PV module with 30 V DC and ranges up to many PV
modules with up to 1500 V DC (Fig. 12.8).
“PV inverters” are inverters, which are designed and built especially for use in
PV systems. During the last 30 years their price has decreased by a factor 10, and
their efficiency has improved from 95% to over 98%.