Striclty for educational purposes Final project in M.Sc. Course for teachers, in the framework of the Caesarea –Rothschild program of the Feinberg Grad School of the Weizmann inst. of Science. Note that ppt may contain copy-righted material and as such any use that can violate such rights will require permission from the © holders.

Rothschild-Weizmann Program “Materials for Energy” Lecturer: Prof. David Cahen January 2014 Moshe Riben & Esty Zemler

Useful Energy from Wave Power Heating by the sun creates wind and the wind creates waves in the ocean – how does it happen?  The sun warms the oceans.  The water evaporates and rises to the atmosphere.  While rising, the water experiences temperature (T) and air pressure (p) differences that change its density.  Gradients in p cause air mass to flow (from high to low p), which is one of the elements that create wind.  Wind, blowing upon the ocean surface creates waves.

Sea wave characteristics:  Waves are formed at the ocean surface.  Waves are formed only at wind velocity, v > 0.5 m/sec.  A wave moves in the same direction as the wind that created it.  The wave velocity is approximately equal to the wind velocity.  A wave’s length and frequency are effected by the wind speed.  Wave height depends on:  The period of time the wind blows  The expanse of water over which the wind blows  Wave height is highest closest to the sea surface, decreasing downwards.

The Challenge: Converting wave power to electrical energy 2:15

While waves move – the water stands still!  When a wave travels through deep water, the water rises up and moves down in a circular manner back to its original position.  As the water gets deeper, the circular movement weakens. Upper water Deep Water

Waves contain two forms of energy:  Potential Energy, E p : energy required to move the water up and down  Kinetic Energy, E K : energy required to move the water in a circular manner m water mass = S · ρ h · 2 λ 4 S water area = =

E P = E K P T = P P + P K P T = 2 · P P Water velocity in the crest of a wave differs from that in the trough. To get the group velocity, divide calculated velocity by 2, and thus :

Unit Check:

World map of wave power around global coastline [kW/m]:

Ashdod coastline 5.5 km

Average presence of deep water (≥ 40 m) waves across Ashdod coastline Weighted mean wave height : (1· · · 6 + 4· 0.5) : 100 = 1.24 m Average time present (%) Height, [m]Wave condition 72.5%~ 1low 21% 2 - 1mediocre 6% 4 - 2high 0.5%Above 4Very high Israel Oceanographic and Limnological Research ( )

v Wave velocity [m/sec] h Wave height [m] T Period [sec] Calm sea Stormy sea (weighted) 5 (estimated) average Hawaii Wave velocity across Ashdod coastline Compared to Makapuu coastline, Hawaii Based on data from the Israel Oceanographic and Limnological Research and SEASUN report

P total Power [kW/m] v Wave velocity [m/sec] h Wave height [m] Calm sea Stormy sea Weighted mean Hawaii Wave power across Ashdod coastline Comparing the Makapuu coastline, Hawaii Based on data from the Israel Oceanographic and Limnological Research and SEASUN report

Wave power efficiency Based on Pelamis Co. devices: 40 snake-like devices spread along 2 km of Britain’s coastline Wave power of 40 kW/m provides 6 kW/m ~15% efficiency) PowerEfficiency 47 kW/m 100%Ashdod coastline waves 7 kW/m 15%“Sea snakes” Wave farm 5.5 kW/m 80% (total of 12%) Converting to electric energy (including heat losses and AC/DC current conversion)

Annual A/C consumption Average number of days in class Daily A/C consumption Number of air-conditioner Daily Energy consumption of 1 A/C Number of classes per day Energy consumption per hour A/C power 3,600 MWh ~ MWh kWh 73.5 kWh 3.5 kW Annual electricity consumption of air conditioning (A/C) in the educational institutes of city of Ashdod: Number of wave farm working days required to provide annual electrical energy for A/C of educational institutions in Ashdod: Farm working days Farm working hours Available energy per hour Required amount of energy h11 MWh3,600 MWh

Data taken from “Strategic program for reducing air pollution and climate preservation – Ashdod”, Leshem Sheffer, February 2009

Total farm working days Required farm working hours (11MWh (per hour Total annual consumption (MWh) Type of consumption ,600 A/C of educational institutions 711,70019,000 Public buildings (all use) 501,20013,000 Traffic &street lights ,000 Water pumping and sewage work 3658,80096,600 Total municipal con- sumption (excluding private households Estimation of wave farm electricity use for several consumption types

Comparison between a hypothetical sea wave-power farm and various Israeli power plants 140 Sea Farms = the Ashdod power plant Coastline length needed – 280 km (Israeli Coastline length – 180 km) Energy produced per year [GWh] Energy produced per day [MWh] Energy produced per hour [MWh] Power [MW] Energy sourcePower Plant Sea waves 1 km of wave farm 60,0002,500 Natural Gas Hadera power plant 37,2001,550 Coal Ashdod power plant 2411 Bio-Gas Ayalon Park (Hiriya) Hydroelectricity Kfar HaNassi Wind Golan Heights wind farm 2411Photovoltaic Kibbutz Ketura

WEC – Wave Energy Converters There are more than 1,000 patented wave energy techniques. There are hundreds of projects at different development levels, as well as a variety of potential techniques – and their number increases. WECs are categorized by:  Location: distance of farm from coastline and water depth.  Method: method for producing energy from the waves – PTO (Power Take-off)

Farm that integrates several technologies: Different WEC (Wave Energy Converter) technologies The concept: wave energy moves turbines, which, in turn, generate electricity : 1:00 0:50 1:20

Attenuator  Long buoys are set along the travelling direction of the wave.  As the buoys move, a hydraulic system operates.  The hydraulic piston creates pressure using oil as a working fluid.  Change in oil pressure drives the turbine, generating electricity.

Attenuator – the technology on which we based our energy calculations

Dimensions: length – 150 m ; Diameter – 3.5 m

Disadvantages that have to be taken into consideration:  Sustainability and Environmental damages:  Damages to the coastline view  Interference with natural habitats – heat emission, oil leakage, noise, magnetic fields  Maintenance:  Corrosion resistance  Repairs in case of damage  Oil changing  Interruptions to sea transportation

Bibliography Drew, B., Plummer, A., & Sahinkaya, M. (2009). A review of wave energy converter technology. Proc. IMechE, Falcao, A. F. (2010). Wave energy utilization: A review of the technologies. Renewable and Sustainable Energy Reviews, 899–918. Ginley, D., & Cahen, D. (2011). Fundamentals of Materials for Energy and Environmental Sustainability. MRS ; Cambridge Univ. Press Henderson, R. (2006). Design, simulation, and testing of a novel hydraulic power take- off system for the Pelamis wave energy converter. Renewable Energy, 271–283. MacKay, D. (2009). Sustainable Energy without the hot air SEASUN Power Systems. (1992). WAVE ENERGY RESOURCE AND ECONOMIC ASSESSMENT. seasun power systems. עיריית אשדוד - היחידה לתכנון אסטרטגי. (2012). שנתון סטטיסטי - אשדוד אשדוד: עיריית אשדוד. רוזן, ד' ס'. (1999). בחינת מיקום מיטבי להצבת כלובי דגים במימי החופין של ישראל בים התיכון. חקר ימים ואגמים לישראל.

Rothschild-Weizmann Program “Materials for Energy” Lecturer: Prof. David Cahen Written by: Moshe Riben & Esty Zemler January 2014