Nivel de conocimiento que tiene el docente, en el ámbito de la gestión del

It may be recalled that an average daily total solar energy intensity of 5.25 KWh/m2/day, on the earth’s surface, and sunshine duration of 6.25 hrs/day is available in Nigeria. It should be noted that a day here refers to 6.25hrs of sunshine, which is about 26% of a normal day. Nigeria has a total land area of about 79.4 x 10¹⁰m² [ECN, 2005]. If, 1% only of the land area is made available for use with a solar – to – electricity system of 5% efficiency, then about 333,480MW of electricity may be generated at 26% capacity factor. One of the challenges to harnessing solar energy to electricity is its variability in intensity through the day, with zero intensity in the nights. However, systems with energy storage, either in thermal energy storage form or electrical energy storage in batteries, would enhance capacity factor. Higher efficiency of solar module is desirable for enhanced electrical energy output as well as for lower land area needed to capture the required solar field for a desired electrical output. Solar electricity generation systems can either be a solar photovoltaic (PV) or a solar thermal system. The electricity generated there from can either be solely dedicated for grid connection, self consumption in homes or for both.

(a) Solar PV System

It is a system that converts the sun’s electromagnetic radiation directly into electricity, usually direct current (dc) electricity. The solar cell is the smallest unit that does this conversion. Solar cells are made of semi-conductor materials, usually silicon, which through photo-electric effect produces an electric current of about 3.5 amps at voltages of 0.4V and 0.5V, when exposed to standard solar radiation intensity of 1000W/m² solar cells are usually connected in series to increase output voltage to a useful level. Usually 36 cells or 72 cells are arranged in series in a module to produce an output of about 18V and 36V, respectively.

Typical I-V characteristic of a solar module is given in Fig. 5. Solar modules are commonly used as flat collectors, enabling them to utilize total solar radiation.

However, concentrator PV (CPV) systems are available, that depend mainly on the direct component of solar radiation. A number of commercial varieties of solar cells are available. They include crystalline silicon, thin film, and others as depicted in Table 1. The modules may be connected to a maximum power point tracking system (MPPT), a grid-tie inverter or battery back-up inverter, depending upon the system, before power gets to the grid. Grid –tie inverters operate only on detection of utility power as is illustrated in Fig. 6. They are designed to shut down automatically when utility supply is not available. They are therefore suitable for sole grid use. Battery back-up inverters manage battery charge via on board charger, and it exports excess energy to the utility grid. They are also capable of supplying power to selected loads during a utility power failure as is illustrated in Fig. 7. They however require anti-islanding protection.

Fig. 8 show a 2,5MW and 5MW solar PV power plants in the Cape Verde island commissioned in 2010.

Proceeding of PTDF – UMYU International Conference on Renewable Energy Katsina 2012 3^rd – 5^th Sept. 2012

© Published By Petroleum Technology Development Fund and Umaru Musa Yar’adua University Katsina

Table 1: Commercially Available Solar Cell Module Types

Source: Mark Hankins, 2010.

(b) Solar Thermal Electricity Generation Systems

These are systems where solar energy is first converted to heat energy, mainly using concentrators. Concentrators can be parabolic, heliostat, paraboloid dish, fresnel lens or plain mirrors depending upon the level of concentration required.

The heat then activates a thermodynamic power cycle (Rankine or Stirling) to produce mechanical energy. The mechanical energy turns an electric generator, producing electricity. Examples of such systems are the 50MW and 20MW solar thermal power plants that are grid connected in Spain and Egypt, respectively.

Fig. 9 shows the 50MW Andosol solar thermal plant with storage in spain The

overall efficiency of such system is determined by the efficiencies of solar thermal collection, turbine and generator as follows:

ηsystem = ηcollector × ηturbine × ηgenerator Typical values:

ηcollector = 0.5 ; ηturbine = 0.45; ηgenerator = 0.9 and so ηsystem = 0.25

(c) Enabling Environment for Grid Connected Solar Electricity in Nigeria.

The National Energy Policy, an instrument in which government expresses its political will in support for harnessing solar energy to enhance the energy supply mix in the country through the active participation of the private sector, was approved by the Federal Executive Council in 2003. The electricity sector in the country was thereafter deregulated and liberalized, for enhanced service delivery through active private sector participation, via the Electric Power Sector Reform Act of 2005. A very vibrant sector regulator, the Nigerian Electricity Regulatory Commission (NERC), was by the Act, also established. However, electrical energy from solar energy is one of the most expensive because of the relatively higher initial investment costs of the technology. Table 2 indicates the investment costs of various power technologies, including that from solar energy. Thus, for solar electricity to penetrate the market, a support scheme, amongst others, referred to as the Feed-in-tariff (FIT) is usually employed. This has, from June 2012, been provided for by the sector regulator, as is indicated in Tables 3 and 4.

Other schemes to incentivize solar electricity production include duty free on imports of equipment, no hindrance to profit repatriation, and Federal Government and World Bank guarantees for power supplied into the grid through the Bulk Electricity Marketer.

Proceeding of PTDF – UMYU International Conference on Renewable Energy Katsina 2012 3^rd – 5^th Sept. 2012

© Published By Petroleum Technology Development Fund and Umaru Musa Yar’adua University Katsina

Table 2: Investment Cost of Power Technologies

S/NO TECHNOLOGY YEAR ON LINE COST ($/kW)

1 Advanced open cycle gas turbine 2008 398

2. Conventional open cycle gas turbine 2008 420

3. Advanced gas/oil combined cycle 2009 594

4. Conventional gas/oil combined cycle 2009 603

5. Distributed generation (base load) 2009 859

6. Distributed generation (peak load) 2008 1032

7. Advanced combined cycle with sequestration 2010 1185

8. Wind 2009 1208

9. Coal-fired plant with scrubber 2010 1290

10. IGCC 2010 1490

11. Conventional hydropower 2010 1500

12. Biomass 2010 1869

13. Geothermal 2010 1880

14. Advanced nuclear 2011 2081

15. IGCC with carbon sequestration 2010 2134

16. Solar thermal 2009 3149

17. Fuel cell 2009 4520

18. Photo voltaic (PV) 2008 4751

Source: www.jcmiras.Net_02

Table 3: Technical Assumptions for Feed-in-Tariffs (2012)

S/N Description Units Assumptions

Wind Solar Small

Hydro Biomass

1 Installed capacity MW 10 5 10 5

2 Capital Cost US$/kW 2,525 5,545 3,500 4,000

3 O&M Cost (Fixed) NGN/MW/Yr 2,900,000 9,570,000 5,655,000 8,370,000

4 O&M Cost (Var.) NGN/MWh 232 87 87 775

5 Capacity Factor % 38 33 60 68

6 Auxiliary Requirement

% 1 1 1 10

7 Economic life Years 25 25 25 25

8 Construction Period Years 3 3 3 3

Source: NERC, 2012

Table 4: Wholesale Feed-in-Tariff Solar Plant

2012 2013 2014 2015 2016

Wholesale contract (N/MWh)

67,917 73,300 79,116 85,401 92,192

Source: NERC, 2012