Energy Research Center

Research

Dec 30th, 2015

Temperature sensitive PSII and promiscuous PSI as a possible solution for

Biomass

Biomass

Studies on the crystal structure of photosystem I prompted us to consider using our knowledge for designing a bioreactor for sustainable hydrogen production. We discovered a marine phage that carries an operon encoding all PSI subunits. The generation, in Synechcystis, of a phage-like PSI, where PsaF and PsaJ subunits were substituted by a PsaJF fusion, enabled the mutated PSI to accept electrons from additional sources like respiratory cytochromes. In this way a novel photorespiration was created, where PSI could substitute for cytochrome oxidase,. The wild-type and mutant synechocistis PSI were crystallized and solved, confirming the suggested structural sequences. We designed a hydrogen producing bioreactor where the novel photorespiration could utilize the organic material of the cell as an electron source for H2 production. We propose in parallel to engineer a Cyanobacterium strain with a temperature sensitive PSII and enhanced rates of respiration. In this way efficient and sustainable hydrogen production could be achieved.

A shematic representation of cyanobacterial bioreactor for sustanable hydrogen production

Research

Dec 30th, 2015

Cogeneration of power and fuel

A combined process for converting renewable organic matter into hydrogen fuel and generating electricity as a by-product, that can reach overall conversion efficiencies of around 50%.

Biomass

Biomass

We have developed an innovative approach for converting renewable organic matter (waste, biomass) into a biofuel (hydrogen, syngas), with the simultaneous generation of electricity. The conversion is carried out at moderate temperatures (400°C – 600°C) and at high pressure using a Super-Critical Water Gasification reaction. The heat input can be obtained from a solar concentrator field such as a trough, tower, or any other suitable heat source. Thermodynamic analysis has shown that overall heat to electricity conversion efficiencies could reach about 50%, exceeding those of known and comparable thermal conversion processes. Were the heat provided by a solar tower, the overall solar energy to electricity conversion efficiency could be close to 30%, compared to less than 20% for current leading solar technologies. We are investigating major technical challenges in implementing this process, including speeding up of the reaction by innovative high performance catalysts, as well as the separation process, both for inorganic materials upstream of the reactor and for the fuel downstream of the turbine.

Collaboration: M. Epstein (WIS)

Support: Israel Ministry of National Infrastructure

Research

Dec 29th, 2015

Photosynthetic Hydrogen Production

The forced delivery of PSI generated electrons to an artificial ferredoxin-hydrogenase fusion enzyme can be used for the mass production of hydrogen gas. This, together with the creation of an engineered PSI for accepting electrons from multiple donors, should make the photosynthetic production of hydrogen a feasible reality.

Biomass

Biomass

Oxygenic photosynthesis underpins the survival of virtually all higher forms of life. Photosystem I (PSI) generates the most negative redox potential in nature. Most of the negative redox potential is stabilized in the form of reduced ferredoxin (Fd) that serves as an electron donor to the enzyme ferredoxin-NADP+-reductase (FNR). Under normal physiological conditions, Fd reduces NADP+ to NADPH via the Fd-FNR complex. NADPH is the main reducing force in the Calvin cycle, in which organic carbon in the form of CO2 gas is fixed into glucose, the main source for organic carbon in nature. In some systems there is competition between FNR and the hydrogenase for the PSI generated electrons. Hydrogenases are present in only part of the photosynthetic world, namely unicellular algae and cyanobacteria, and are expressed only under anaerobic condition.

To be able to shuttle most of the PSI generated electrons to the hydrogenase, the competing processes must first be eliminated or bypassed. In our research we will be interfering with the formation of the naturally occurring Fd-FNR complex by over-expressing artificial ferredoxin-hydrogenase fusion enzymes. Our aim is to force the delivery of PSI generated electrons to the artificial ferredoxin-hydrogenase fusion enzyme and in this way be used for mass hydrogen gas production. An additional aspect of the study, carried out in Prof. Nelson’s Laboratory, is the creation of an engineered PSI which, as a result of subunit fusions inspired by PSI from marine phages, should be promiscuous in accepting electrons from multiple donors, thereby increasing its throughput. The two technologies combined should make photosynthetic hydrogen production a feasible reality.

collaboration Dr. Iftach Yacoby of The Center for Biomedical Engineering (MIT)

Figure 1: Photosynthetic hydrogen production. During the natural course of photosynthesis (A), electrons from Photosystem I (PSI) are shuttled by ferredoxin (Fd) mostly to NADP⁺ reductase (large red arrow) and utilized for energy storage by the plant or alga. In our approach (B) fusion of Fd to hydrogenase should shuttle more electrons directly towards H₂ production.

* This research is being carried out in collaboration with Dr. Iftach Yacoby of The Center for Biomedical Engineering (MIT)

Research

Dec 29th, 2015

Organic and Bio-inspired Solar Cells – from single molecules to the complete

Chemical and engineering tools for integrating bio and molecular layers into photovoltaic cells.

Biomass

Biomass

Research in our lab is focused on constructing a bio-inspired solar cell based on incorporating photo-active bio-molecules and specially designed polymers into a solid-state device. To this end we use doped macro-molecules or modified Photo System 1 proteins (synthesised by Carmeli), and water-soluble conducting polymers (Herrmann) to construct the bio-inspired photovoltaic cell. In this systems-approach we develop chemical and engineering tools that allow for the integration of the soft bio and molecular layers into the solid-state photovoltaic device. These tools include the p- and n- type doping of macro-molecules, the use of surface chemistry to form self-assembled monolayers of the molecules, enhancement of the photovoltaic signal by plasmonic interactions, and the development of polymer and inorganic

collaboration with Andreas Herrmann

Research

Dec 29th, 2015

Photosynthetic electron partitioning between [FeFe]-hydrogenase and ferredoxin

Biomass

Biomass

Photosynthetic water splitting, coupled to hydrogenase-catalyzed hydrogen production, is considered a promising clean, renewable source of energy. It is widely accepted that the oxygen sensitivity of hydrogen production, combined with competition between hydrogenases and NADPH-dependent carbon dioxide fixation are the main limitations for its commercialization. Here we provide evidence that, under the anaerobic conditions that support hydrogen production, there is a significant loss of photosynthetic electrons toward NADPH production in vitro. To elucidate the basis for competition, we bioengineered a ferredoxin-hydrogenase fusion and characterized hydrogen production kinetics in the presence of Fd, ferredoxin:NADP⁺-oxidoreductase (FNR), and NADP⁺. Replacing the hydrogenase with a ferredoxin-hydrogenase fusion switched the bias of electron transfer from FNR to hydrogenase and resulted in an increased rate of hydrogen photoproduction. These results suggest a new direction for improvement of biohydrogen production and a means to further resolve the mechanisms that control partitioning of photosynthetic electron transport.

Research

Dec 29th, 2015

Wind Turbulence Structure Lab

Wind

Wind

Natural fluctuations and changes in wind conditions severely handicap the efficiency of wind-generated power. Furthermore the noise produced by rotating turbines is a major contributor to noise pollution. To address these problems we in this laboratory have produced the first MEMS-based probe capable of providing critical aerodynamic data under the rigors and conditions of high wind speeds and turbulence. We have further developed techniques that will allow us to significantly improve the structure and design of wind turbines, thus enabling us to produce, in Israel, the first in a new generation of non-conventional turbine blades.

Research

Dec 29th, 2015

Climate Change in Israel: A Climatological-synoptic Study

Climatic trends in Israel 1975-2010 - temperature, heat-stress and rainfall fluctuations.

Wind

Wind

Israel is situated on the edge of the desert belt, and displays extreme differences in climate between the north and the south of the country. In the north, Mediterranean conditions prevail while areas in the south are dry and arid. These climatic regions are characterized by sharp changes and fluctuations in weather patterns, including heat waves and dry spells which have severe impacts on the environment. Our ability to verify or disprove predicted trends based on accumulated data over past decades is therefore of great importance.

Our research is based on the analysis of climate trends, for example temperature, heat stress and rainfall fluctuations, from data collected over the past 35 years. A significant warming trend, in excess of the global rate, has been noted in the summer season, as well as an aggravation in heat waves and conditions of heat stress.

Regarding the rainfall regime, a general decrease in precipitation and a reduction in the number of rain days have been noted, though insignificant in most of the regions, presumably due to the large inter- and intra-annual variations characterizing this region. However, a lengthening of dry spells was found significant over most of the country.

Changes in the location of the aridity borders of 300 mm and 200 mm, critical for dry farming, are being studied. Results indicate that the size of the arid area has been expanding, especially over the last 20 years, at the expense of the Mediterranean temperate area. The contribution of changes in the occurrence of the regional synoptic systems to explain inter-annual variations and also long-term trends in temperature, heat stress and rainfall regimens is also being carefully studied. It was found that inter-decadal variations in the synoptic and large-scale factors explain considerable part of the rainfall and temperature variations.

Research

Dec 29th, 2015

Active Flow Control opens up major opportunities for increasing the efficient

The development of a turbine providing increased performance efficiencies at lower wind speeds and with significantly reduced noise levels will enable the positioning of wind turbines also in built-up areas.

Wind

Wind

“Wind is one of the cleanest sources of natural energy provided by nature,” says Professor Avi Seifert of the Tel Aviv University School of Mechanical Engineering.

Wind energy is closely related to solar energy since winds are created by the solar heating of the atmosphere. Current technology for producing power from wind is not as effective as it could be, as wind turbines work efficiently only within a certain range of wind speeds. This shortcoming limits the efficient functioning of the units and also poses serious limitations on where they can be placed. Professors Seifert. Miloh and Kribus are working on the development of a wind turbine that will be capable of working efficiently at much lower speeds. This technology, known as Active Flow Control, has been in development at the Tel Aviv University’s Meadow Aerodynamics Laboratory for over two decades and, as Seifert explains, “is able to alter the air flow at the turbine blade surface with a small input of energy in the right place and at the right time, producing an increase in overall performance.” When working at maximum efficiencies, wind turbines using Active Flow Control technology could be placed in areas of lower wind speeds, thus opening up a wider range of possibilities and opportunities for the use of wind power.

Another drawback is the high levels of noise produced by existing turbines, making it almost impossible to place wind turbines in or near residential areas. Seifert, in collaboration with Professor Tuvia Miloh of the School of Mechanical Engineering, their PhD student Oksana Stalnov and another scholar Dr. Thorsten Lutz at the University of Stuttgart, Germany, are working on reducing the noise levels of wind turbines using Active Flow Control. This would allow for turbines to be placed in and around built-up areas without causing a disturbance.

Seifert sees wind as a clean source of energy with enormous potential, untapped in many places as in Israel. “With increased levels of efficiency, wind turbines could be smaller in size, quieter and more flexible, allowing them to be placed closer to homes. This would significantly increase our ability to harness energy from wind,” Seifert concludes.

Another major area of application for the Active Flow Control technology, under development at Prof. Seifert’s laboratory, is reducing the aerodynamic drag (resistance) of large trucks driving at high speeds on the freeways, thereby significantly improving their fuel efficiency.

Research

Dec 20th, 2015

Nano Antennas & Carbon Nanotubes

When it comes to converting solar energy (sunlight) to electricity the silicon cell has one major limitation – it utilises only 40 % of the total energy available from sunlight.

Solar

Solar

When it comes to converting solar energy (sunlight) to electricity the silicon cell has one major limitation – it utilises only 40 % of the total energy available from sunlight. This means 60 % of the energy goes to waste! The reason is that silicon works with the higher energy frequencies only, wavelengths shorter than that of infra red. This limitation in the use of silicon has led our scientific team to engage in some brilliant and uniquely innovative research, based on the use of antennae rather than silicon cells to capture the longer, unused solar energy wavelengths. Sunlight being a form of electromagnetic radiation could be picked up by antennas in the same way as other electromagnetic radiation and used to produce an electric current. To achieve this miniature antennas would have to be constructed, nanometers in length, each corresponding to specific wavelength in the solar spectrum. Here the carbon nanotube provides the ideal solution. The carbon nanotube (built from carbon atoms) would also solve another major problem, namely the conversion of AC current as generated by high frequency solar energy into DC current. When configured as a diode the carbon nanotube is able to do this. These two elements, the nano antennas and the carbon nanotubes, represent significant breakthroughs in the field of solar energy utilisation, and major strides are being made in this exciting new avenue of research. Indeed, the components necessary for achieving these results have already been produced in the laboratory and the conversion of certain wavelengths of light to electricity have been successfully demonstrated .

(a) (b)

Figure 1:HRSEM image of (a) a nano-antenna array (b) A single CrAu dipole antenna

(a) (b)

Figure 2: HRSEM images of (a) CNT diode: carbon nanotubes grown between electrodes. (b) Bowtie nano-antena arrays (image and a single antenna (inset).

Research

Dec 20th, 2015

Direct Steam Generation in Solar Power Plants

Studying the flow-patterns of steam-water mixtures in order to overcome problems of instability, will help to increase the efficiency of solar power plants.

Solar

Solar

Up to now commercial power plants have been using oil as the primary heating fuel in absorption tubes, with steam being generated in secondary heat exchangers. This process is not efficient due to the need for additional heat exchangers, which result in additional heat loss during the process of heat transfer from oil to steam.

Direct Steam Generation (DSG) within the collectors themselves is a potentially more efficient and less costly process, achieved by eliminating oil as the indirect secondary heating medium and the elimination of heat exchanges and other equipment necessary for transferring heat from the oil to water/steam.

The reason Direct Steam Generation has not been used up to now is because of our incomplete understanding of two-phase flow behavior within the absorption pipes, and the fear of the possibility of circumferential temperature distribution, instability and uneven flow distribution.

Our research is aimed at studying the behavior of steam-water mixtures flowing in parallel pipes in order to find ways of overcoming the problems of instability and flow maldistribution in these complex systems. The knowledge thus obtained will allow for the development of solar power plants with higher efficiencies.

Figure 2: Solar power plant in Californea

Research

Dec 20th, 2015

Single molecule solar cells

Induce efficient charge separation (within a certain material) by light.

Solar

Solar

We believe that in order to understand the fundamentals of these processes, especially in organic solar cells, we must try to understand them at the most well characterized, organized, and smallest system.

We therefore suggest to construct and study single molecule solar cells.

As a first stage we have developed two types of molecular junctions, on-edge and suspended wire junctions that enable interaction of light with the embedded molecules. These junctions are based on several thousands of molecules. We can prove using two types of spectroscopy, inelastic electron tunneling spectroscopy and transition voltage spectroscopy, that indeed the molecules are inside the junctions and act as the active part.

We use Raman spectroscopy to prove that indeed we can squeeze light into the junctions. Based on Raman intensity we estimate the plasmon enhancement of the electromagnetic field in our structures, which could over ~100!

We show solar cell performance based on current rectification at optical frequencies using the suspended wire junctions.

We have developed a new measurement scheme to precisely measure the plasmonic enhancement of light inside our junctions based on the magnitude of current rectification. According to these measurements plasmonic enhancement of the electromagnetic field in our junctions is ~500!

We are now moving to the next stage of performing similar experiments at the single molecule level. Here various types of molecules, specifically designed for efficient charge separation would be used.