Hybrid Systems Power Generation
Background
For years, the power supply to isolated areas where it is unfeasible to build a
grid connection, has been done with systems that use fossil fuel generators
(diesel, gasoline, LPG ...). Wind and solar energy sources are ubiquitous,
freely available and their use can be done in a way that respects the
environment. The falling cost of photovoltaic systems and wind, along with the
rising price of petroleum products has made these technologies to be already
competitive not only in developing countries with limited grid, but also in many
applications in developed countries. Although the availability of sufficient
wind is not ensured everywhere and its action is more unpredictable than solar
energy, the combined use of these renewable energy sources has clear advantages
in cost, flexibility and availability, limiting dependence on energy produced by
fossil fuels.
A hybrid power system consists of two or more power sources for powering loads
or consumers. Since the late 70's of XX century the combination of diesel
generators with wind systems has been used to power remote locations. Later on
diesel-photovoltaic systems and wind-photovoltaic-diesel have appeared as common
solutions. The combination of renewable energy systems without using fossil fuel
generation, has become popular in remote applications where noise, space and
maintenance of generators is not feasible, and in recent years, substantial
price petroleum products has increased the attractiveness of solutions based
only on renewable energy. However, the use of these hybrid systems presents
specific challenges when the application is professional type, where the system
requirements (availability, operability, etc.) are different from those that can
claim a domestic application.
Application of hybrid systems
The most common applications for professional-type hybrid systems are those
related to telecommunications systems, monitoring and telemetry systems, or
signalling.
These systems are located in areas far from urban centers, where it is costly to
build the conventional power grid. In many cases access is difficult, so it is
very expensive requiring regular maintenance of generators. These are
applications that have consumption between 1 and 100 kWh per day and which by
their nature require good availability. In lower power systems with the most
common solutions would be purely solar or wind, and for systems with higher
consumption would be usual complement generators that use a fossil fuel.
In telecommunications systems are used in repeaters and mobile base stations,
satellite ground stations, TV gap-fillers, etc.
Hybrid relay stations (solar, wind)
Base Station (BTS) mobile phone (solar-wind-diesel)
DVB-T Gap-filler (solar-wind)
The hybrid power solutions for radio systems are especially favorable for
several reasons. Radio systems are often located at high locations to maximize
coverage and visibility with connection points, which makes them points for good
wind conditions, but away from main roads. On the other hand, these tend to be
locations where it is available a tower or mast for installation of antennas,
which in many cases to use this structure to secure the wind turbine, reducing
costs by sharing a very important element.
In the study Green Power for Mobile by the GSMA (association of all GSM / UMTS
worldwide) in 2008, it was estimated there were about 1500 base stations powered
by renewable energy, and about 10000 more planned. It estimate that up to 2012
each year about 75000 new stations installed without connection to the
electricity grid in developing countries and of these, 50% will be powered by
renewable energy, mainly solar and wind energy.
Click to enlarge
Considering a BTS with an average consumption of 800 W, the investment could
be paid in three years with a single solution or just wind PV and 2.5 years if
the system were hybrid (see chart).
Hybrid systems are used in very important applications for monitoring and
cathodic protection in locations where solar and wind energy production can be
complementary.
Monitoring applications