PEC Solar Energy Technology (MEC-2) UET-Taxila Overview of High Temperature Solar Power Production Prof. Dr. A. R. El-Ghalban Department of Mechanical Engineering Prepared by University of Engineering and Technology Taxila, Pakistan

PEC Solar Energy Technology (MEC-2) UET-Taxila Technology Overview  Electric power generation.  Hydrogen production  High temperature can be achieved by concentrating solar radiation using various mirror configurations. High temperature heat can be used in the following applications;

PEC Solar Energy Technology (MEC-2) UET-Taxila Electric power generation  Using concentrating systems solar power plants produce electric power by converting the sun's energy into high-temperature heat.  The heat is then channeled through a conventional generator.  The plants consist of two parts: One that collects solar energy and converts it to heat, and Another that converts heat energy to electricity.

PEC Solar Energy Technology (MEC-2) UET-Taxila  Concentrating solar power systems can be sized from (10 kilowatts up to 350 megawatts).  Some systems use thermal storage during cloudy periods or at night.  Others can be combined with natural gas and the resulting hybrid power plants provide high-value, dispatchable power.  Concentrating solar power plants generate their peak output during sunny periods when peak electricity demand occurs as air conditioning loads are at their peak. Electric power generation

PEC Solar Energy Technology (MEC-2) UET-Taxila Technology Overview  These attributes, along with world record solar-to- electric conversion efficiencies, make concentrating solar power an attractive renewable energy option in the sunbelt regions worldwide.  There are three kinds of concentrating solar power systems. This classification according to the way how they collect solar energy.  Trough systems,  Dish/engine systems, and  Power tower systems.

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems  In such systems the sun's energy is concentrated by parabolic curved, trough-shaped reflectors onto a receiver pipe running along the inside of the curved surface.  This energy heats oil flowing through the pipe, and the heat energy is then used to generate electricity in a conventional steam generator.  A collector field comprises many troughs in parallel rows aligned on a north-south axis.

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems  This configuration enables the single-axis troughs to track the sun from east to west during the day to ensure that the sun is continuously focused on the receiver pipes.  Trough designs can incorporate thermal storage— setting aside the heat transfer fluid in its hot phase— allowing for electricity generation several hours into the evening.  Currently, all parabolic trough plants are "hybrids," meaning they use fossil fuel to supplement the solar output during periods of low solar radiation.

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems  Parabolic concentrators have been successfully operating commercially since 1984, including the largest solar power plant of any kind, the 350 MW plant Solar Energy Generating Systems.

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Systems  A dish/engine system uses a mirrored dish (similar to a very large satellite dish).  The dish-shaped surface collects and concentrates the sun's heat onto a receiver, which absorbs the heat and transfers it to fluid within the engine.  The heat causes the fluid to expand against a piston or turbine to produce mechanical power.  The mechanical power is then used to run a generator or alternator to produce electricity by an electric generator or alternator.

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Systems  Dish/engine systems use dual-axis collectors to track the sun.  The ideal concentrator shape is parabolic, created either by a single reflective surface or multiple reflectors, or facets.  There are many options for receiver and engine type, including Stirling engine and Brayton receivers.  Dish/engine systems are not commercially available, although ongoing demonstrations indicate good potential.

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Systems  Individual dish/engine systems currently can generate about 25 kilowatts of electricity.  More capacity is possible by connecting dishes together.  These systems can be combined with natural gas and the resulting hybrid provides continuous power generation.  The dish-Stirling system works at higher efficiencies than any other current solar technologies, with a net solar-to-electric conversion efficiency reaching 30%.

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Systems  One of the system’s advantages is that it is “somewhat modular,” and the size of the facility can be ramped up over a period of time.  That is compared to a traditional power plant or other large-scale solar technologies that have to be completely built before they are operational.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers  By collecting solar energy during daylight hours and storing it in hot molten salt, solar power towers give utilities an alternative method for meeting peak loads.  The receiver collects the sun's heat in a heat-transfer fluid (liquid salt), which is used to generate steam for a conventional steam turbine located at the foot of the tower for production of electricity.  The liquid salt at 290°C is pumped from a cold storage tank through the receiver, where it is heated to 565°C and then on to a hot tank for storage.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers  When power is needed from the plant, hot salt is pumped to a steam generating system that produces superheated steam to power a turbine and generator.  From the steam generator, the salt is returned to the cold tank, where it is stored and eventually reheated in the receiver.  They are unique among solar technologies because they can store energy efficiently and cost effectively.  They can operate whenever the customer needs power, even after dark or during cloudy weather.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers  Power towers operate by focusing a field of thousands of mirrors onto a receiver located at the top of a centrally located tower.  With thermal storage, power towers can operate at an annual capacity factor of 65%, which means they can potentially operate for 65% of the year without a backup fuel source. Without energy storage, solar technologies like this are limited to annual capacity factors near 25%.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Hydrogen Production  Steam Methane Reforming  Steam methane reforming is a possible process to produce hydrogen. Methane is reformed at elevated temperature and pressure to produce a syngas (mixture of H 2 and CO). CH 4 +H 2 O Heat (206 kJ/ mole) 2H 2 + CO  The reforming reaction is carried out in a reformer containing tubes filled with nickel catalyst at temperatures between 500ºC and 950ºC and a pressure around 30 atmospheres.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Hydrogen Production  Coal Gasification  Like steam methane reforming, coal gasification proceeds by a treatment of coal feedstock with high temperature steam (1330ºC) to produce syngas (mixture of H 2 and CO). Coal (carbon source) + H 2 O H 2 + CO + impurities  The heat required for this gasification step comes from controlled addition of oxygen, which allows partial oxidation of a small amount of the coal feedstock.

PEC Solar Energy Technology (MEC-2) UET-Taxila Coal Gasification  Because of this, the reaction is carried out in either an air-blown or oxygen-blown gasifier. The oxygen blown gasifier must be supplied with O 2 from an independent air purification system.

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Hydrogen Production  Sulfur-Iodine Cycle  In the sulfur-iodine cycle, a heat source, possibly a solar dish, provides the heat necessary to drive three coupled thermo-chemical reactions.  The coupled reaction system takes water as an input and through a series of reactions involving sulfur and iodine produces H 2 and O 2 as output. Process flow sheets have been developed for heat sources at 850 °C and 950°C.  The S-I cycle is described by the reactions:

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Hydrogen Production 2H 2 O + SO 2 + I 2 Heat (-216 kJ/ mole) H 2 SO HI (< 120 o C) H 2 SO 4 Heat ( 371 kJ/ mole) H 2 O +SO 2 + ½ O 2 (> 800 o C) 2HI Heat ( 12 kJ/ mole) H 2 + I 2 (> 300 o C) Net Effect H 2 O H 2 + ½ O 2

PEC Solar Energy Technology (MEC-2) UET-Taxila Thank you

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Generation The Idea of Solar Driven ORC

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems

PEC Solar Energy Technology (MEC-2) UET-Taxila Trough systems

PEC Solar Energy Technology (MEC-2) UET-Taxila  The cost for such prototype unit (25 kW) is about $150,000. Once in production the cost could be reduced to less than $50,000 each, which would make the cost of electricity competitive with conventional fuel technologies. Dish/Engine Systems

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Systems

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Receiver

PEC Solar Energy Technology (MEC-2) UET-Taxila Dish/Engine Plant

PEC Solar Energy Technology (MEC-2) UET-Taxila Stirling engine

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers

PEC Solar Energy Technology (MEC-2) UET-Taxila Solar Power Towers