The solar panels at Totana power plant in Spain generate 2 GWh of electricity per year
The fully-automated 1 MW Totana plant operates for around 2200 hours per year to generate 2.2 GWh of electricity per annum from several rows of moving PV panels, which track the position of the sun in order to maximize energy capture. Tracking systems can produce up to 35 per cent more power than fixed PV panels, says power automation specialist, ABB, equivalent to an extra two hours of operation per day. The trackers move in two axes, powered by small electric motors.
ABB was asked to build the plant within six months in order to meet a deadline to be eligible for new Spanish feed-in tariffs for PV-generated electricity. The company delivered the system in four months.
As a turnkey installation, ABB was responsible for ground and civil works, together with supply and installation of trackers, inverters, control and SCADA systems, transformers and switchgear. The PV modules were supplied by a Spanish company using solar cells manufactured in China.
Visiting the plant in the middle of a sunny day in September, the panels were operating at an efficiency of 83 per cent, compared to an annual average of 77 per cent.
With a 25-year design life, the system has a calculated payback period of between seven and eight years; this figure depends critically on the power plant delivering the very last percentage point of performance to the grid. This is where ABB sees its strength – the company supplies all the equipment needed to maximize production.
At Totana, nine inverters transform the generated power from 400 V DC to 600 V AC. These inverters operate at efficiencies of 97-98 per cent at full load. However, the efficiency falls very dramatically at part load, so the automatic control system selects the right combination of inverters to operate at any one time – so that inverters are working as close to full load as possible.
The voltages are increased to 20 kV at the substation where, again, two heavy duty transformers are used to optimize efficiency and deliver for maximum security of supply.
All of this happens automatically, without a personnel presence at the site – except for security and, twice year, to wash down the panels. According to ABB, 1 MW generating modules like the one at Totana are easily connected together to increase generating capacity, and come pre-assembled, factory-tested and containerized for rapid installation, anywhere in the world.
PV and concentrating solar technology
Aside from supplying complete PV generating modules such as the Totana installation, ABB says it provides power and automation products and systems for each stage of any major solar power process – all the way from robotic systems that help manufacture PV cells to complete power and automation packages for large-scale concentrating solar thermal power (CSP) plants.
CSP will be vital to the realization of projects like Desertec, where the Desertec Industrial Initiative, a consortium of commercial partners including ABB, was formed this year to take the concept of very large-scale power from the deserts of North Africa towards reality.
One of ABB’s main roles is to find a way of transmitting large volumes of power from desert locations which are remote from the load centres, with acceptably small losses – thus the development of high voltage direct current (HVDC) systems.
Tracking systems can produce up to 35 per cent more power than fixed PV panels, equivalent to an extra two hours of operation per day
The company has been working in solar power since its early involvement in the 1990s, developing an automation platform for the world’s first test facility for CSP technologies, the Plataforma Solar de Almería in Spain.
Since then, ABB has provided solutions for solar power projects around the world and has developed technologies to maximize the productivity and reliability of both PV and CSP systems. CSP uses mirrors to reflect sunlight onto fluids, which heat up and then pass through a heat exchanger to generate steam, drive a turbine and generate electricity. Both PV and CSP are important and growing areas.
According to ABB, in 2008, grid-tied solar PV grew by 70 per cent, and the capacity of utility-scale solar PV plants – larger than 200 kW – tripled to 3 GW. China recently announced that it will develop a 2000 MW PV farm in the Mongolian desert, to be completed in phases by 2019, which is expected to provide enough electricity to power three million Chinese homes.
The CSP market grew by 15 per cent. In the CSP segment, ABB provides complete power and automation solutions for entire installations. The solutions include technology that enables each of the thousands of parabolic troughs in the solar fields to collect maximum energy; instrumentation and control systems for the heat transfer tubes, thermal storage tanks and power plant; electrical balance of plant for the power block; and electrical equipment that feeds the power reliably into the power grid.
Examples of ABB solutions for CSP plants include the two largest installations in Europe – Andasol 1 & 2 and Extresol 1 & 2 in Spain, generating 50 MW of electricity per unit. Other examples are eSolar in the USA and the 150 MW Hassi R’Mel plant in Algeria, which is one of the first power plants in the world to integrate solar and combined-cycle power generation in a single facility.
Small-scale with smart potential
ABB is also a global supplier of power and automation products for smaller scale solar power installations used in industrial, commercial and residential buildings using fixed modules or solar trackers installed on a building or on adjacent land.
Products include all the key components for operating the solar trackers, converting the direct current into alternating current, protecting the entire system from surges, and delivering power to the grid.
This work on small-scale decentralized power generation can be extended into the ‘smart grid’ arena. ABB says it is currently running a pilot project to develop a network control system that integrates automated metering, decentralized power generation, multi-directional energy flows, and energy trading systems into a single, smart power grid.
The solution is based on ABB’s existing Network Manager, the familiar platform for energy trading systems and for the monitoring and control of power generation, transmission and distribution networks.
The solar power supergrid
The Desertec concept envisages an interconnected Europe, Middle East and North Africa in which huge amounts of electricity are generated in the region’s deserts and transported to consumers throughout the region via a solar power supergrid.
The idea grew out of ABB’s early development of HVDC transmission technology, a system invented to provide an efficient means of transmitting large amounts of electricity over long distances or under the sea.
Back in 1992, ABB power transmission experts drew up a map showing the potential of harnessing renewable energy created in Europe, the Middle East and North Africa to meet the growing power needs of the region. The plan ties together wind farms, hydropower, biomass, geothermal and a series of solar plants across North Africa, connected to Europe using high efficiency HVDC power links.
It is the central vision of the Desertec Foundation, an international non-governmental organization to transform vast quantities of solar energy from the world’s deserts into sustainable, emissions free electricity to help meet the growing needs of an expanding global population.
This grand vision took a further step towards realization in July of this year when ABB and 11 other companies joined forces to create the Desertec Industrial Initiative. The main goal of the initiative is to work on the feasibility, financing and construction of the project, in which a large number of networked solar thermal power plants cover the Middle East, North Africa and Mediterranean Europe.
The aim is to produce by 2050 enough emissions-free electricity to make a significant contribution to satisfying Europe’s power requirements, while at the same time serving the power needs of the source countries. The resultant savings in greenhouse gas emissions will be considerable.
Two technologies have been singled out by the Desertec Foundation as the most efficient and sustainable to generate and transport this huge volume of electric power: HVDC and CSP plants.