Configuration E is based primarily on the use of alternative
energy sources such as solar photovoltaic (PV) modules, wind generators and hydroelectric
generators. These configurations can be economical alternatives to the high cost of
extending utility lines to remote areas. Since the purchase cost of these systems is
usually higher on a per-watt basis than conventional electricity sources, special
attention should be given to the use of energy efficient appliances. Electric space
heating, cooking, water heating and refrigeration should be avoided and replaced with
propane or other fuel sources. Typical configurations are described below using a
number of sub-categories.
- Configuration E1 - Solar
PV Module Stand-Alone System
- Configuration E2 - Small
AC PV Module with Utility Intertie, no Battery Backup
- Configuration E3 - Solar
PV Stand-Alone Hybrid with Engine-Generator Backup
- Configuration E4 - Solar
PV Stand-Alone Hybrid with Wind/Hydro Generator
- Configuration E5 - Same as E4
except with pre-packaged control panel
- Configuration E6 - Larger PV
Module with Utility Intertie, no Battery Backup
- Configuration E7 - Larger PV
Module with Utility Intertie and Battery Backup
Configuration E1 is based
totally on solar energy for all electric generation. To provide power when the sun
is not shining, battery storage is used.
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above to enlarge
Advantages of this E1 configuration include:
 | simplicity relative to other "E" configurations
|
| completely independent of utility power grid
|
| few if any mechanical parts to wear out or to maintain
|
| system can be designed to allow expansion later by adding solar modules and
battery cells if electrical loads grow
|
Some disadvantages of this E1 arrangement are:
| prolonged cloudy conditions that discharge batteries will interrupt electrical
power
|
| batteries are used which may (depending on type) require manual watering,
terminal cleaning and equalization charges throughout their life
|
| batteries have a finite cycle life and will need replacement after a certain
number of years
|
| electrical loads must be minimized for this system to be attractive
|
Configuration E2 is based
primarily on utility power with supplemental onsite solar electric generation.
Special AC PV solar modules are used which consist of a PV module plus an integral AC
inverter designed for utility intertie. The inverter is specially designed to
shutdown during utility power outages to avoid dangerous backfeed into the grid. The
solar generated electricity offsets some of that normally provided by the utility.
Depending on system size and load fluctuations it is possible to "sell" excess
electricity back to the utility.
click thumbnail image
above to enlarge
Advantages of this E2 configuration include:
| easy to install, the ultimate in simplicity
|
| additional AC PV modules can be added as funds allow simply by daisy chaining
them together
|
| no battery storage required which reduces initial system cost and ongoing
maintenance
|
| no dc interconnecting components required since output is totally ac
|
| each module works independent of the others
|
| no dangerous backfeed into the grid during power outages
|
Some disadvantages of this E2 arrangement are:
| electricity from PV modules not available as a backup during power outages unless
many additional components are added
|
| some utilities require that a second kWh meter be installed to monitor onsite
generation and so that it can be purchased back at a different rate
|
Configuration E3 is similar to
E1 except for an AC engine generator set that can be used to recharge the batteries during
prolonged periods without sun light or when AC load demand is larger than normal.
click thumbnail image
above to enlarge
Advantages of this E3 configuration include:
| completely independent of utility power grid
|
| prolonged cloudy conditions that discharge batteries will not interrupt
electrical power
|
| system can be designed to allow expansion later by adding solar modules and
battery cells if electrical loads grow
|
Some disadvantages of this E3 arrangement are:
| batteries are used which may (depending on type) require manual watering,
terminal cleaning and equalization charges throughout their life
|
| batteries have a finite cycle life and will need replacement after a certain
number of years
|
| electrical loads must be minimized for this system to be attractive
|
| engine generator requires maintenance
|
Configuration E4 uses a
diversity of alternative generation sources to increase the availability of onsite
power. The solar PV generated power is supplemented by wind and/or
hydroelectric. The feasibility of using these additional resources is highly
dependent on site conditions. But, where these other resources are available, they
can create a very advantageous mix.
click thumbnail image
above to enlarge
Advantages of this E4 configuration include:
| diversified energy sources decrease likelihood of prolonged loss of all power
generation
|
| completely independent of utility power grid
|
| system can be designed to allow expansion later by adding solar modules, wind or
hydro generators and battery cells if electrical loads grow
|
Some disadvantages of this E4 arrangement are:
| prolonged loss of generation that discharge batteries will interrupt electrical
power
|
| batteries are used which may (depending on type) require manual watering,
terminal cleaning and equalization charges throughout their life
|
| batteries have a finite cycle life and will need replacement after a certain
number of years
|
| the moving parts in wind and/or hydro turbines require a certain amount of
maintenance
|
| electrical loads must be minimized for this system to be attractive
|
Configuration E5 is similar to
E4 except for the pre-packaged control panel which simplifies installation. The
Whisper wind generators made by World Power Technologies include this kind of control
panel. This configuration can also use a diversity of alternative generation
sources to increase the availability of onsite power. The solar PV generated power
is supplemented by wind and/or hydroelectric. The feasibility of using these
additional resources is highly dependent on site conditions. But, where these other
resources are available, they can create a very advantageous mix.
click thumbnail image
above to enlarge
Advantages of this E5 configuration include:
| diversified energy sources decrease likelihood of prolonged loss of all power
generation
|
| completely independent of utility power grid
|
| pre-packaged control panel is self-contained and simplifies installation and
operation of system |
Some disadvantages of this E5 arrangement are:
| control panel must be matched to size of wind generator and has limited options
for expansion short of complete replacement
|
| prolonged loss of generation that discharge batteries will interrupt electrical
power
|
| batteries are used which may (depending on type) require manual watering,
terminal cleaning and equalization charges throughout their life
|
| batteries have a finite cycle life and will need replacement after a certain
number of years
|
| the moving parts in wind and/or hydro turbines require a certain amount of
maintenance
|
| electrical loads must be minimized for this system to be attractive
|
Configuration E6 is based
primarily on utility power with supplemental onsite solar electric generation. It is
similar to Configuration E2 except that standard DC PV solar modules are used with a
separate AC inverter designed for utility intertie without batteries. The
inverter is designed with advanced protective
systems to shutdown during utility power outages to avoid dangerous backfeed into the
grid. The solar generated electricity offsets some of that normally provided by the
utility. Depending on system size and load fluctuations it is possible to "sell"
excess electricity back to the utility.
click thumbnail image
above to enlarge
Advantages of this E6 configuration include:
| additional DC PV modules can be added as funds allow as long as they are within
the inverter capacity
|
| no battery storage required which reduces initial system cost and ongoing
maintenance
|
| no dangerous backfeed into the grid during power outages
|
Some disadvantages of this E6 arrangement are:
| electricity from PV modules not available as a backup during power outages unless
many additional components are added
|
| some utilities require that a second kWh meter be installed to monitor onsite
generation and so that it can be purchased back at a different rate
|
Configuration E7 is based
primarily on utility power with supplemental onsite solar electric generation. It is
similar to Configuration E6 except that battery backup is added for providing AC power
during utility outages. Optional engine generator backup and/or supplemental wind or
hydroelectric generation can be used. The control and distribution design and
installation can be simplified by using an Integrated Power Panel which contains all the
utility inter-active inverter(s), ground fault protection, charge control, diversion load
control, overcurrent protection and disconnects. The inverter is designed with
advanced protective systems that
detect utility power outages to avoid dangerous backfeed into the grid. When a power
outage occurs, the inverter(s) separate from the grid and continue to power essential
loads via a sub-panel. The solar generated electricity offsets some of that normally
provided by the utility. Depending on system size and load fluctuations it is possible to
"sell" excess electricity back to the utility.
click thumbnail image
above to enlarge
Advantages of this E7 configuration include:
| additional DC PV modules can be added as funds allow as long as they are within
the inverter and power panel capacity
|
| automatic battery backup for essential AC circuits during power outages
|
| no dangerous backfeed into the grid during power outages
|
| pre-packaged control panel is self-contained and simplifies installation and
operation of system
|
Some disadvantages of this E7 arrangement are:
| batteries are used which may (depending on type) require manual watering,
terminal cleaning and equalization charges throughout their life
|
| batteries have a finite cycle life and will need replacement after a certain
number of years
|
| some utilities require that a second kWh meter be installed to monitor onsite
generation and so that it can be purchased back at a different rate
|
| 
