The book “Corrosion and Materials in the Oil and Gas Industries”, edited by Reza Javaherdashti, Chikezie Nwaoha and Henry Tan, has been published by CRC Press/Taylor and Francis LLC, USA.

Since James Watt, a Scottish inventor, invented the steam engine, human civilization relies more and more on energy supply. The re-rise as an international superpower and the global energy crisis are challenging China and the world. We are at a transitional age. On the one hand, we see the technology advances in exploration and development of oil and gas, a depleting resource; and the growth in handling ageing and decommissioning. On the other hand, we see ideas and plans for new energy structure in the future.

The discussions here relate to a conference I am chairing, the International Symposium on Energy Challenges and Mechanics, held in this summer at Aberdeen, Scotland, the energy capital of Europe. This theme is about energy challenges and the role of mechanics as a means for seeking solutions, involving multiple disciplines in technology, science and management. The topics include both fossil fuels and many different forms of renewable energy. In addition, we will discuss the role of mechanics in issues related to energy efficiency, safety and environment.

The discussion sessions developed include:

I. Fossil fuels related

• Reservoir simulation
• Reservoir stimulation and production
• Subsea engineering
• Subsea integrity
• Drilling process and technology

II. Renewable energy related

• Marine energy
• Bioenergy
• Wind energy
• Photovoltaics
• Flexible solar cells
• Numerical and experimental research on the durability of photovoltaic modules
• Hydropower and dam engineering
• Lithium ion batteries
• Energy storage
• Energy harvesting
• Fuel cells
• Nano-energy
• Energy and superconductivity
• Graphene-based nanotechnology for energy applications
• Porous materials and structures for energy applications
• New energy vehicles

III. Energy efficiency, safety and environment

• Energy and environment
• Thermal barrier coatings for energy efficient engines
• Carbon dioxide capture and utilization
• Nuclear energy

IV. General

• Energy future
• Material simulation for energy applications
• Energy conversion and fuels
• Training for the Energy Industry
  

Professor Michael Kelly FRS FREng, Prince Philip Professor of Technology, University of Cambridge, gave the Closing Plenary at the 2nd International Symposium on Energy Challenges and Mechanics, hosted by the North Sea Conference and Journal.

Michael wrote the speech into an article, “Future energy needs and engineering reality”. The paper was published in the Journal of Energy Challenges and Mechanics.
http://www.nscj.co.uk/JECM/JECM1-3.html

The paper link is
http://www.nscj.co.uk/JECM/PDF/1-3-1-Kelly.pdf

This is the first serious attempt to review the progress over the last 20 years towards decarbonizing the world economy by 80% by 2050. Taking general lessons from the introductions of new technologies over the past 200 years, one can see that the targets are not going to be met, and in some cases matters are being made worse.

4th International Symposium on Energy Challenges and Mechanics - working on small scales

Session 11: NANOMECHANICS (http://nscj.co.uk/ecm4/sessions/session11.html)

Mechanical properties are crucial to better understand the final properties of applicable materials. From this point of view Nanomechanics is an important Nanoscience branch, which allows to study fundamental mechanical properties at the nanoscale. This knowledge is key point for the application of novel materials.

All research investigations done recently in the field of Nanomechanics are welcome to be discussed in this session in order to better understand mechanical behavior of the materials at the nanoscale.

3rd International Symposium on Energy Challenges and Mechanics - towards a big picture
7th-9th July 2015, Aberdeen, United Kingdom, the Energy Capital of Europe

Conference website
Conference Guide
Programme
Plenary lectures
Parallel sessions

Since James Watt, a Scottish inventor, improved the efficiency of steam engine, human civilization relies more and more on a steady energy supply. Today, the world is poised on the brink of two historic energy transformations: replacing oil with electricity in transportation, and replacing high carbon, finite-supply coal and natural gas with renewable wind, solar, marine and biomass energies for electricity production. This symposium is about current state of the art small scale technologies being applied to solve energy challenges,

http://nscj.co.uk/ecm5/index.html

Since James Watt, a Scottish inventor, improved the efficiency of steam engine, human civilization relies more and more on a steady supply of energy. Today we are at a transitional age. On one hand, we see technology advances in the exploration and development of oil and gas, a depleting resource; we see growth in handling aging and decommissioning. On the other hand, we see ideas and plans for the future's new energy structure. This symposium is about energy challenges, the underlying energetic basis (mechanics) for society, involving multiple disciplines in technology, science, management and policy-making. The topics include both fossil fuels and many different forms of renewable energy. In addition, we will discuss issues related to energy policy and economy, energy efficiency, safety and environment. The purpose is to gain a big picture about energy challenges and solutions.

http://nscj.co.uk/ecm6/index.html

As an example, here we discuss implant-associated infection from the mechanics point of view on bacteria adhesion affected by the biomaterial surface roughness:

1.    Implant-associated infection, a leading cause of failure in many biomedical devices, is caused by adhesion of bacteria to the surface of biomaterials. Implant-associated infection is difficult to treat, for example, joint replacement infections may occur deep around the artificial implants.

2.    Microbial adhesion and subsequent biofilm formation are mediated by van der Waals attractive forces, electrostatic repulsive forces, and surface hydrophobicity. The predominance of these forces is dependent on the distance between the microorganism and the surface, usually at distances greater than 50 nm van der Waals forces are the main factor, while at closer distances (10−20 nm) a combination of both van der Waals forces and electrostatic interactions controls cell adhesion.

3.    Implant surface roughness is an important property relevant for the bacterial adhesion process, with the irregularities of the surfaces normally promoting bacterial adhesion and colonization.

4.    For metals used in medical implants, the desired surface roughness is usually below 10 nm. At nanometre scale rough surface promotes friction, hence reduces the mobility of the bacteria; this sessile environment expedites the biofilm growth.

5.    To reduce the roughness, surface nanotopography of medical implants is an important approach that can control the extent of bacterial adhesion.

6.    Surrounding the implant are soft and hard tissues, as well as the corrosive body liquid. Whether the roughness of an initially nanoscale smooth surface will grow or decay is of crucial importance for implant devices.

7.    For a stress metal implant under shallow chemical etching, the roughness with spatial frequency below a critical value grows while the roughness of higher frequency decays.

8.    A rougher surface had lower constraint for electrons to escape from peaks, resulting in lower chemical potential.

References:

Tan, H. (2016) In vivo surface roughness evolution of a stressed metallic implant. Journal of the Mechanics and Physics of Solids, 95, 430–440.

Truong, V.K., Pham, V.T.H., Medvedev, A., Lapovok, R., Estrin, Y., Lowe, T.C., Baulin, V., Boshkovikj, V., Fluke, C.J., Crawford, R.J., Ivanova, E.P. (2015) Self-organised nanoarchitecture of titanium surfaces influences the attachment of Staphylococcus aureus and Pseudomonas aeruginosa bacteria. Appl. Microbiol. Biotechnol. 99, 6831-6840.

Ryu, J.J., Shrotriya, P. (2015) Mechanical load assisted dissolution response of biomedical cobalt-chromium and titanium metallic alloys: Influence of in-plane stress and chemical environment. Wear 332-333, 662-668.

Desrousseaux, C., Cueff, R., Aumeran, C., Garrait, G., Mailhot-Jensen, B., Traoré, O., Sautou, V. (2015) Fabrication of acrylonitrile-butadiene-styrene nanostructures with anodic alumina oxide templates, characterization and biofilm development test for Staphylococcus epidermidis. PLoS ONE 10, Article number e0135632.

Yoda, I., Koseki, H., Tomita, M., Shida, T., Horiuchi, H., Sakoda, H., Osaki, M. (2014) Effect of surface roughness of biomaterials on Staphylococcus epidermidis adhesion. BMC Microbiology 14, 234-240.

Wang, J., Yao, J., Gao, H. (2012) Specific adhesion of a soft elastic body on a wavy surface. Theoretical and Applied Mechanics Letters, Article 014002.

Conference website: http://fm2017.nscj.co.uk/index.html

Introduction: These are lands nurtured generations of mechanicians such as Sir Isaac Newton PRS, Sir William Thomson Lord Kelvin, James Watt FRS FRSE, etc. On this land, we meet and quest again the frontiers of mechanics and the interactive boundaries with many other disciplines. This conference is split from the previous International Symposium on Energy Challenges and Mechanics (ECM1, ECM2, ECM3, ECM4, ECM5 and ECM6). The focus is on the applications of mechanics, not only in energy but also in other areas such as biomedical devices, microfluidics and nanofluidics, flexible electronics, biological fluid dynamics, extreme loading scenarios, environmental flows, etc.

ECM6 delegates national distribution

Conference theme song: We are a light - by Nils Elders © All rights reserved.

Conference website: http://energy7.nscj.co.uk/

Introduction: This event is the Seventh International Symposium on Energy; it combines previous two symposia (International Symposium on Energy Challenges and Mechanics - working on small scales; International Symposium on Energy Challenges and Mechanics – towards a big picture) into one. The conference involves multiple disciplines in technology, science, management and policy-making. The topics include both fossil fuels and many different forms of renewable energy. In addition, it addresses issues related to energy policy and economy, energy efficiency, safety and environment. The purpose is to gain a complete view about energy challenges and solutions between these different disciplines and from a global perspective.

ECM6 delegates national distribution

Conference theme song: We are a light - by Nils Elders © All rights reserved.

I am teaching Subsea Integrity for the MSc students majoring in Subsea Engineering at the School of Engineering, University of Aberdeen. This is a course that combines the fundamental principles (corrosion, fracture, fatigue and material selection) with the industry applications (subsea integrity management and implementation, cathodic protection, case studies on subsea reliability and engineering assurance).

Teaching time schedule

Week 1 (Tuesday, 2/2):  Subsea integrity management and implementation (industrial lectures, IICORR Ltd)
Part 1 – Subsea integrity management (Mark Wilson), movie, pdf
Part 2 – Subsea integrity implementation (Dr. George Watson), movie, pdf
 

Week 2 (Tuesday, 9/2): Corrosion I (Dr. Tan)
Part 1 – Subsea integrity module, movie, pdf
Part 2 – Electrochemical cell, movie, pdf
 

Week 3 (Tuesday, 16/2): Corrosion II (Dr. Tan)
Part 1 – Subsea corrosion, movie, pdf
Part 2 – Corrosion protection, movie, pdf

 
Week 4 (Tuesday, 23/2): Corrosion III (Dr. Tan)
Part 1 – Corrosion rate, movie, pdf
Part 2 – Polarization, movie, pdf
 

Week 5 (Tuesday, 2/3): Fracture I (Dr. Tan)
Part 1 – Stress intensity factor, movie, pdf
Part 2 – Fracture toughness, movie, pdf

 
Week 6 (Tuesday, 9/3): Subsea engineering integrity and assurance (industrial lecture, Ji Wen, BP plc), pdf
Part 1 – movie
Part 2 – movie

 
Week 7 (Tuesday, 16/3): On Project and Tutorial 1 (corrosion) solutions (Dr. Tan)
Part 1 – Project
Part 2 – Tutorial 1 (corrosion) solutions

 
Week 8 (Tuesday, 23/3): Cathodic protection (industrial lectures, IICORR Ltd)
Part 1 – Cathodic Protection Monitoring (Richard Holt), movie, pdf
Part 2 – An Industry Perspective on Cathodic Protection Design (Tim Queen), movie, pdf

Week 9 (Tuesday, 20/4): Fracture II / Fatigue I (Dr. Tan)
Part 1 – Environment assisted cracking, movie, pdf
Part 2 – Fatigue fracture, movie, pdf
 

Week 10 (Tuesday, 27/4): Subsea integrity (tentative)
            (industrial lectures, Martin Harley and Dave Flett, Talisman Energy UK Ltd)

 
Week 11 (Tuesday, 4/5): Fatigue II (Dr. Tan)
Part 1 – Corrosion fatigue, movie, pdf
Part 2 – Tutorial 2 (fracture) solutions, movie, pdf
 

Week 12 (Tuesday, 11/5): Corrosion/Fracture/Fatigue (Dr. Tan)
Part 1 – Tutorial 3 (fatigue) solutions, movie, pdf
Part 2 – Summary

Mission Statement
To facilitate communication and a rich exchange of knowledge among academia, industry, and research societies whose works involve mechanics.

Introduction
These are lands nurtured generations of mechanicians such as Sir Isaac Newton PRS, Sir William Thomson Lord Kelvin, James Watt FRS FRSE, etc. On this land, we meet and quest again the frontiers of mechanics and the interactive boundaries with many other disciplines. This conference is split from the previous International Symposium on Energy Challenges and Mechanics (ECM1, ECM2, ECM3, ECM4, ECM5 and ECM6). The focus is on the applications of mechanics. Detailed topics can be found here.

Materials such as sedimentary rocks, pharmaceutical tablets, plastic bonded explosives, biscuits, concretes, nacre, solid propellants, seashells and asphalts can be treated as particulate composites that consist of particles of high volume fraction, matrixes of thin layer and interfaces of high specific surface area. Mechanical behaviour of highly packed particulate composites is the theme of this issue of Journal Club forum.

1. Sedimentary rocks, covering almost the entire ocean floor and about three-quarters of the Earth's land area, are made of sediments cemented or compacted together by a particular force or process over time. Damaged sedimentary rocks, such as those during oil and gas extraction or subsea oil spilling, may cause manmade earthquake. On the other side, studies on the behaviour of sedimentary rocks can bring benefits to petroleum industry such as in improving the drilling efficiency. Behaviour of sedimentary rocks are important in many fields of earth sciences, partly because they relate to the sudden rock failure that contributes to earthquakes, and partly because they forms permeable paths for fluid flow in fault zones (Gudmundsson et al., in press)

2. For pulsatile drug delivery, an osmotic tablet consists of a medical core surrounded by a coating made of a material that is water-insoluble but permeable. The pressure build-up in the core pushes the coating for drug release (Rahemba et al., 2009). For a coating made of particulate composites, the percolation of interfaces can provide a controllable way for drug delivery.

3. Energetic materials such as plastic bonded explosives and solid rocket propellants consist of particles of high volume fraction embedded in a polymeric binder. During slow loading, crack propagation is mainly along interfaces, particles are not fractured rather the crack deviates over or under them. Burning occurs on the pressured surface, the network of debonded interfaces allows hot gas access to increased internal surface area and thereby increases the burning rates, which further accelerate the debonding. The network close to the surface triggers the burn--to-violent-reaction (BVR) transition (Gould et al., 2009).

4. In many structured food applications, mixed biopolymer gels are utilised that exhibit typical emulsion-like phase-separated microstructures, which include spherical particles of one phase (e.g. maltodextrin) within a continuous matrix of the second (e.g. gelatin). One of the greatest challenges in the food industries is to develop products that can fracture in a pre-designed way so that they can provide the required function (Brink et al., 2007).

5. A concrete is made of a cement matrix that bonds particles of different size (gravels and sands) and fills the interstitial space. Sudden debonding and networking of interfaces causes the brittle weakness; chemical and nuclear plants can be at risk from earthquake since the protecting concrete structures can be vulnerable.

6. Nacre, produced by some molluscs as an inner shell layer and known as the “mother of pearl”, consists of about 95% (weight) inorganic aragonite platelets and a few percent of organic biopolymer, forming a brick-and-mortar like network; when under attack the network reorganize to spread out the energy of the blow across the shell layer. Further, aragonite platelets are also particulate composite materials consists of nanograins and biopolymer binder, as discovered in an Atomic Force Microscope observation (Li and Huang, 2009). This two-scale (micro-nanoscale) ceramic/polymer composite material is of an extraordinary beauty, very strong and resilient.

References:

Gudmundsson A, Simmenes TH, Larsen B, Philipp SL (in press) Effects of internal structure and local stresses on fracture propagation, deflection, and arrest in fault zones. J. Struct. Geol.

Rahemba TR, Bell S, Connolly EK, Waterman KC (2009) Use of scoring to induce reproducible drug delivery from osmotic pulsatile tablets. Pharm. Dev. Technol. 14:548–555.

Brink J, Langton M, Stading M, Hermansson AM (2007) Simultaneous analysis of the structural and mechanical changes during large deformation of whey protein isolate/gelatin gels at the macro and micro levels. Food Hydrocolloids 21:409–419.

Gould PJ, Porter D, Cullis IG (2009) Predicting the damage/failure transition in polymer-bonded explosives. Proceedings of the 9th International Conference on Mechanical and Physical Behaviour of Materials under High Rate Loading, DYMAT 2009, EDP Sciences, pp. 1629-1633.

Li X, Huang Z (2009) Unveiling the Formation Mechanism of Pseudo-Single-Crystal Aragonite Platelets in Nacre, Phys Rev Lett, 102, 075502.

DISCUSSION THEMES 

• Assessing the potential of ageing infrastructure to provide the same level of service as newly constructed facilities
• Identifying the key threats to the integrity of a pipeline in later life
• New solutions for old pipelines: revealing how new technologies can
  help ensure reliability of older infrastructure and assessing the
  future outlook for mature pipes
• Taking the necessary steps to make sure that older pipelines are operated within regulatory requirements
• Tackling the inspection difficulties associated with ageing pipes

Oil & Gas Pipeline Integrity Management Summit, 7 - 8 October 2010, Aberdeen, UK
Roundtable discussion: Re-assessing ageing pipeline infrastructure to ensure safety, integrity and reliability
Discussion leader: Dr. Henry Tan

This is the discussion blog for the MSc course "Fundamental Safety Engineering and Risk Management Concepts" lectured at the School of Engineering, University of Aberdeen. This course is a core module for the following Postgraduate Taught Programmes:
1. Subsea Engineering; 2. Renewable Energy; 3. Oil and Gas Engineering; 4. Safety and Reliability Engineering

Since this blog is very congested now, you are encouraged to post on sub-blogs for each topic chosen. 

Discussion Topic 1: Rank top ten severe accidents in energy sector

Discussion Topic 2: Is nuclear power safe for humans and the environment?

Discussion Topic 3: Is fracking for shale gas safe and without damage to community environment? Should it be banned?

Discussion Topic 4: If the Piper Alpha disaster occurred today, discuss the current safety legislative regime that will apply.

Discussion Topic 5: In recent years, millions of solar panels have been placed on roofs around the world. Discuss how safe are they? Discuss the hidden pollution caused by solar panels.

Discussion Topic 6: Discuss safety in wind energy.

Discussion Topic 7: Discuss safety considerations in wave energy system.

Discussion Topic 8: Subsea integrity and reliability management

Discussion Topic 9: Safety and risk management in oil and gas industry

Discussion Topic 10: ONGC Mumbai High Accident (July 27, 2005 @ West Coast of India

Discussion Topic 11: Why is the FAR and SIR measures of fatality considered poor measures from the organisation perpective

Discussion Topic 12: Post Macondo underwater technology

Discussion Topic 13: Safety, Reliability and Integrity Mangement Processes and the Human Factor effect

Discussion Topic 14: Discuss safety in biofuels

Discussion Topic 15: Carbon emissions trading: How viable?

Discussion Topic 16: Global dimming and Global warming, hazardous effect of green house gases on our planet earth

Discussion Topic 17: Should Arctic drilling activities be halted until the Safety and Technology are improved?

Discussion Topic 18: The perceived conflict between safety and production

Discussion Topic 19: The April 16, 1947 Texas city fire disaster

Discussion Topic 20: ALARP concept and health and safety of personel, equipments and the work environment. Friends or foe.

Discussion Topic 21: Safety Integrity Level (SIL) of a system is important. What are the methods in place to assess the SIL of any system?

Discussion Topic 22: The role of safety in view of world energy forecast: striking a future balance

Discussion Topic 23: Implication of the offshore industry toward "zero harmful discharge"

Discussion Topic 24: Safety in Hydropower

Discussion Topic 25: The constant struggle between HSE legislation and human stupidity

Discussion Topic 26: The dangers associated with young and inexperienced workers in the workplace

Discussion Topic 27: Geothermal Energy a clean, safe, environmentally friendly and sustainable energy source

Discussion Topic 28: Your view on iMechanica Safety Engineering and Risk Management Debate

Discussion Topic 29: Tackling occupational hazards in developing countries

Discussion Topic 30: Extending the life of pipeline in the North Sea what are the Safety & Risk challenge

Discussion Topic 31: Prescriptive case, Safety case and the furture of Legislation

Discussion Topic 32: Decommissioning of aged Platforms and Pipelines in the North Sea - Risks and Challenges

Discussion Topic 33: Discuss the future of Biomass as an Alternative Source of Energy- Risks and Challenges

Discussion Topic 34: Can the application of Redundancy Increase Safety and Reliability in the oil and gas industry?

Discussion Topic 35: A different approach to the basic R = P x C formula

Discussion Topic 36: Deep Sea Disposal of Oil and Gas Installations – Acceptable risk

Discussion Topic 37: Reliability in the wake of a mega-stor

Discussion Topic 38: Lessons- how are these capture

Discussion Topic 39: Proposed EU regulation on offshore oil and gas safet

Discussion Topic 40: Does the value placed on human life have an effect on safet

Discussion Topic 41: MyAberdeen versus iMechanica

Discussion Topic 42: Potential and Safety Issues concerning Biogas

Discussion Topic 43: Unsafe acts/conditions during routine tasks in platforms/offshore and how to avoid them

Discussion Topic 44: Inherent safety in process safety management – a practical approach

Discussion Topic 45: Managing the risks and issues associated with a depleting reservoir

Discussion Topic 46: Is it safe to leave the abandoned oil and and gas wells?

Discussion Topic 47: Effectiveness of using RBD, FTA, ETA and Bayesian network in modelling failure of equipments in the industry

Discussion Topic 48 (sub-branch): Safety issues during transportation and distribution of oil and gas.

Discussion Topic 49: Safety issues during drilling operations

Discussion Topic 50: Shale Gas Harmful or not, Economical or not

Discussion Topic 51: Energy landscape of the future and the risks associate

Discussion Topic 52: Human Factors in Process Safety

Discussion Topic 53: Health, safety, environmental and cost issues regarding operation, disposal, and re-use of decommisioned plants

Discussion Topic 54: Quality Assurance/Control -the influence on Safety

Discussion Topic 55: Can the applications of Ergonomics Improve Work Place Health and Safety?

Discussion Topic 56: How safe is using a Personal Floatation Devices (PFDs) in an offshore platform or Helicopter Travel?

Discussion Topic 57: Why did macondo happen and changes it brought to health and safety laws

Discussion Topic 58: Discuss the safety and environmental issues of unconventional crude oil exploration

Discussion Topic 59: Discuss the Strategy of Fire Safety and Prevention in Offshore Installation

Discussion Topic 60: Discuss the Prevention of Slips, Trips and fall in the work place

Discussion Topic 61: Reactive Hazards

Discussion Topic 62: Discuss the Emergency Water Landing in the North Sea

Discussion Topic 63: Discuss the risks and challenges involved in working in a confined space.

Discussion Topic 64: Discuss the risks and challenges involved in simultanous operations or co-activities in Oil and Gas activities.

Discussion Topic 65: Excavation Work in Onshore Pipeline Crowded Areas - Risks and challenges

Discussion Topic 66: Discuss the risks and challenges involved in working at heights

Discussion Topic 67: Discuss the safety aspects associated with using divers in offshore operations

Discussion Topic 68: Discuss Body Mechanics and use of Tools in an Offshore Drilling Platform

Discussion Topic 69: The essence of performing FMEA and FMECA in Safety and Risk Management

Discussion Topic 70: Take a break, relax

other topics

You are welcome to initiate new discussion topics. If you are a student in my class “Fundamental Safety Engineering and Risk Management Concepts” and want to start a new discussion topic, you can do the following:
1. post a new blog entry on iMechanica of your proposed discussion topic;
2. email me (h.tan@abdn.ac.uk) the blog address;
3. then I will setup the link between the main discussion blog here and your blog.

Here contains information about how to register and post. about
When you have difficulty with posting comments, read node/3132

People from outside of the class are very welcome to join our debate!

Safety Engineering and Risk Management Debate 2012

Discussion Topic 1: Rank top ten severe accidents in energy sector

Rank top ten severe accidents in energy sector, and investigates their causes and consequences. Discuss the following:
 (1)    What were the physical/technical circumstances that led to the accident?
 (2)    What were the main underlying causes?
 (3)    Why did the accident result in: (i) So many fatalities; (ii) So much harm to the environment etc.?
 (4)    What factors contributed to the escalation of the accident?
 (5)    What were the legal consequences of the accident? 

Safety Engineering and Risk Management Debate 2012

Discussion Topic 2: Is nuclear power safe for humans and the environment?

Safety Engineering and Risk Management Debate 2012

Discussion Topic 3: Is fracking for shale gas safe and without damage to community environment? Should it be banned?

Safety Engineering and Risk Magement Debate 2012

Discussion Topic 4: If the Piper Alpha disaster occurred today, discuss the current safety legislative regime that will apply.

Safety Engineering and Risk Management Debate 2012

Discussion Topic 5: In recent years, millions of solar panels have been placed on roofs around the world. Discuss how safe are they? Discuss the hidden pollution caused by solar panels.