Hydropower is the single largest source of renewable energy in the world, representing a staggering 70% of global renewable energy. Hydropower is produced whenever water flows through a turbine on its way from the mountains back to the ocean. Popular forms of hydropower include dams, tidal, run of river and pumped storage. The primary benefits to hydropower include the low cost of operation, flexibility to adapt to changing energy demands, and zero emissions created during operation. Hydropower is expected to continue to grow at around 3% per year as global energy demands continue to rise. As energy demand continues to increase, so too does the need to monitor, inspect and repair infrastructure associated with hydropower plants. Inspection class remotely operated vehicles (ROVs) provide the perfect means to efficiently and safely inspect dams, reservoirs and river-ways. Here are a five ways ROVs are used in the hydroelectric power industry:
Inspect intake screens:
Whenever water enters a hydropower plant it must first pass through an intake screen meant to filter out fish, weeds, trash and other floating objects from entering a plant’s turbines. These screens must be routinely inspected and cleared of debris to ensure optimal flow. The screens themselves may become damaged or rusted over time. These issues are best identified with the use of underwater inspection class ROVs which allow more frequent inspections at a lower price point and without risk to divers, especially in high flow areas.
Hydropower plants can prove to be a challenging environment in which to perform visual inspections underwater. The high rates of water flow can create a significant amount of turbidity which clouds the water with so much suspended particulate matter that the water appears hazy or muddy. To navigate and map these surroundings, sonar is almost always a requirement. Inspection class ROVs are often outfitted with sonar imaging devices to give an accurate picture of dam walls or the bottom of a reservoir.
Inspecting dam walls:
Failure risks for dams is a very real concern for those living down river and in a very few cases have resulted in catastrophic loss of life. Regular inspection of dam walls, even after hydroelectric decommissioning, is a first line defense against failure risk. Checking for stress fractures, cracks, or other signs of degrading structural integrity can be accomplished through visual inspection with an ROV. ROVs are maneuverable and precise enough to travel up and down, or left and right along an inspection surface, and can stay underwater for the duration of a mission.
Environmental impact and monitoring studies
Every time a dam or reservoir is constructed there is an environmental impact to native wildlife and habitat. With the help of an inspection class ROV, plant owners and environmentalists alike can keep track of the impact and restoration efforts surrounding the construction, operation and decommissioning of a hydroelectric dam project.
Search & Recovery
An unfortunate reality of dam security is the unauthorized access by those unknowingly putting themselves at risk of injury or death. The combination of extreme heights and fast running water can end in disaster for those who don’t treat dams with caution. The ability to rapidly deploy underwater search and recovery operations using inspection class ROVs can greatly aid in times of need.
These are just a few of the ways inspection class ROVs can be used around hydropower. To learn more about Aquabotix and hydropower, visit us at HydroVision 2017 this week, June 27-29, 2017 in Denver, CO at the Colarado Convention Center, Booth #404.
Ask a remote-operated-vehicle (ROV) aficionado what industries these handy little tools have had the most impact on, and the answers will be varied and interesting. Some will immediately name fisheries and aquaculture, where ROVs let even small operators put mobile, flexible, sensor-enhanced eyes on even their most remote underwater operations. Others would favor the transportation industry, where ROVs make major contributions to port security and vessel hull inspections. Relatively few people, however, unless they had industry knowledge backing them up, would name one of the industries where ROVs have had a major and still growing impact: energy production.
To be sure, the energy market is an enormous and enormously varied set of operations, and it is true that ROVs play a small or nonexistent role in many of the industry’s subfields. Nobody expects ROVs to be a major player in coal mines, for example (though they are handy in investigating flooded sections of mine, a very hazardous condition where nobody wants to risk a human diver…)
There are three basic areas in which ROVs play a major role: installation and investigation of offshore windfarms. Installation and investigation of the hydraulic systems of nuclear plants, and inspections of dams – many types of dams, of course, but most relevant here are the major construction achievements that produce local electrical generating capacity, i.e. hydropower.
You may notice something rather fundamental about these three parts of the energy industry: they are all carbon-neutral or low-carbon energy production systems, and thus are important tools in reducing global warming.
Hydropower is among the oldest approaches to renewable energy, and is far older than its relatively recent adaptation to produce electricity. Preindustrial civilizations have used the power of running water to pump water uphill, to irrigate crops, and to turn machinery. In modern times, giant hydroprojects like the Hoover Dam produce thousands of megawatts of electrical power, enough to serve millions of households, at a relatively reasonable environmental cost. Unfortunately, while the Earth has plenty of water and plenty of gravity, the requirements of hydropower for particular configurations of these resources means that the generating capacity of the natural world is more or less known, and fixed – and the “good spots” are already taken. Hydropower produces more than 1,000 Gigawatts (that’s a thousand megawatts) – about a sixth of the world’s total generating capability. Because hydropower generally requires building large dams that hold enormous quantities of water – usually conveniently located just upstream of enormous population centers – the safety monitoring and maintenance of the dam system is of the utmost priority. ROVs, of course, bring the costs of maintenance and inspection down drastically, further increasing the economic sensibility of hydropower as one of the major components of the global energy economy.
In the eyes of many, nuclear power could not be more diametrically opposed to hydropower. But in fact, depending on your point of view, a number of fundamental similarities are clear. First, although neither hydropower or nuclear power are free of environmental costs, those costs tend to be fixed cost that arise from having the industry exist at all, not costs that double every time the installed generating base doubles. Second, both nuclear and hydropower are baseline generation systems, meaning that they are always available. Third, both forms of generation tend to have catastrophic, but extremely rare, failure cases. If Hoover Dam bursts, an entire downstream city will die. If a Soviet-era nuclear plant goes critical, half of Eastern Europe could be irradiated. This combination of low expenses, high reliability, and rare disaster cases encourage us to think of these forms of power as being *perfectly* reliable, when in fact they are anything but. How to push those systems towards increased stability? Again, with more frequent and more capable monitoring.
If hydropower is the revered ancestor, still trusted but unable to keep up with the demands of his hungry children, and nuclear power is the disliked but economically essential rich cousin whose fortune keeps the family from starvation, then surely offshore windpower is the angsty, emotionally involved younger sibling – a source of infinite potential and hope for the future that is, unfortunately, wrapped in often problematic presentation right now. Windpower has an enormously high undeveloped potential for power generation, at an environmental cost that is minimal if not negligible. (Just the surface layers of the atmosphere could generate 20 times the current TOTAL human energy usage.) Unfortunately, as with hydropower, the easy spots – that is, the places where a huge turbine farm isn’t out of place - are being used for other projects. And that means that wind power has to move offshore, where the real estate tends to be heavily discounted on account of being a thousand feet beneath the ocean. And although it’s possible for us to build infrastructure in the ocean on this scale, it’s not cheap and it’s not easy – and again enter ROVs, keeping costs down, keeping human divers out of harm’s way, and providing more information for project engineers about safety and performance.
It would be an exaggeration to say that without ROVs, we can’t get to a lower-carbon, warming-mitigated world economy. But it wouldn’t be an exaggeration at all to say that ROVs are making major contribution to the energy economy’s attempt to get us over the carbon-footprint hill and into the low-carbon, high-energy promised land.
Nuclear power is an important source of electricity in many parts of the world. With more than 500 reactors either in operation or under construction, nuclear power accounts for about 11% of the world’s electrical power generation. Although there are environmental concerns surrounding nuclear power, nuclear electricity generation produces no atmospheric carbon dioxide; as concerns about global warming become more acute, it is likely that this method of generating electricity is going to become more prevalent.
Nuclear power works by using the heat from a controlled nuclear reaction to boil water – in essence, an atomic power plant is a giant teakettle. The steam from the boiling water turns a turbine, which generates electricity. The steam is then recaptured, allowed to condense back into liquid water, and run back through the reactor system. Many reactors also use water to cool the operating machinery of the plant itself. All of this water, of course, must be piped and conveyed and stored. The hydraulic systems of a nuclear power plant are more complicated than the actual nuclear reaction machinery itself, and contain vast amounts of water. Of course, those hydraulic systems need inspection and repair work.
Unfortunately, however, the environment of a nuclear power plant’s cooling systems tend to be unfriendly to human beings, to put it mildly. Since the water is drawn into the plant and boiled, the water that discharges from the condensing system is still very hot. Radiation levels in the coolant system, while nowhere near what they would be in the containment chamber of the reactor, can be significantly higher than the background level. Finally, the conditions in the hydraulic systems tend to be cramped and constricted. All of these things make putting human divers into a plant’s hydraulic system a really bad idea. At the same time, the exceptionally clear water conditions inside the cooling system make visibility exceptionally good.
ROVs, while not immune to radiation (electronic devices can be damaged by high levels of ionizing radiation), can handle levels of radiation that would make a human being sick or increase their cancer risk without any problems. This allows plant operators to use ROVs to inspect cooling tanks for leaks, check the walls of reservoirs, test the condition of intake pipes and storage dams, and measure water conditions in holding tanks. The use of ROVs in hazardous areas eliminates the need to put human divers at risk and also eliminates the need to dewater areas of the plant (often necessitating an expensive and time-consuming shutdown of the plant) for visual inspections.
ROVs are also of use in decommissioning nuclear plants. When a nuclear plant reaches the end of its life, there is a great deal of inspection and demolition work that must go into decontaminating the site. ROVs can be used for visual surveys of underwater structures at the site, to conduct radiometric surveys of potentially contaminated areas, and even assist in demolishing contaminated areas underwater. Tethered ROVs actually perform very well in these areas, because the umbilical connection means that the need for sophisticated electronics on the ROV is reduced – more of the sensitive electronic components are safely away from the contaminated area, in the control console or PC being used to run the ROV. Combined sonar/radiologic surveys of contaminated areas reduce the cost of the physical demolition work, as workers have a perfect map of the area and know which spots are “hot”.
As nuclear power grows more important in providing our civilization’s energy needs, ROVs will play a major role in ensuring that this form of electrical generation is safe and economical.
Nuclear Power Plant Diagram By Tennessee Valley Authority (tva.com) [Public domain], via Wikimedia Commons
An offshore windfarm is an array of power-generating wind turbines usually built in the shallow water close to the coastline. Offshore wind power has three main advantages over land-based wind power: the wind directly offshore is usually stronger and steadier than it would be inland, the windfarm can be placed very close to the urban area that will be using the power, and there is less “not-in-my-backyard” opposition from local residents, since the local residents are mainly fish. The primary disadvantage of offshore wind farms is that they are much more expensive to build and maintain than other forms of low-carbon power generation.
The European Union is by far the world leader in offshore wind generation, with about 10 gigawatts (GW) of capacity. China and Canada both have modest windfarm operations and India is working on windfarm development, while the United States will open its first operational windfarm in late 2016 off Block Island in Rhode Island. Despite the high costs of offshore wind power development, projections of installed capacity continue to grow; the European Union expects to have between 20 and 40 GW of capacity online by 2020, and China perhaps optimistically expects to have 30 GW by the same year.
The primary component of an offshore windfarm is the wind turbine - the huge set of blades set atop an enormous pole, which spin as the wind blows. To achieve maximum effect, turbines need to be high off the surface of the water, so the pole must be very long - more than 200 meters. Such a large structure must be anchored extremely securely to the seabed, and there are a number of ways in which this is done. Regardless of the exact nature of the structural engineering, the underwater structures of offshore wind turbines need to be inspected on a regular basis.
In the United States, offshore windfarm inspections will be under the oversight of the Department of the Interior’s Bureau of Safety and Environmental Enforcement (BSEE). BSEE’s draft standards draw heavily on the experience of the United Kingdom, and lay out an inspection regime that concentrates a great deal of attention on the turbines themselves, naturally enough. However, the underwater bases of the turbines come in for their share of attention as well.
BSEE draft standards will likely require that windfarms be inspected on an annual basis, with 20% of a farm’s individual turbines and foundations inspected in each annual cycle. Critical components should be evaluated annually, while less critical areas can be inspected as infrequently as every five years. Foundations need to be checked for structural health, bioaccumulation, scouring, spalling, and corrosion. Subsea cables need to be inspected for damage due to sand, marine animals, or anchoring. BSEE suggests that general visual inspections can be carried out by ROVs, while close visual inspections need to be done by human divers.
BSEE standards are likely to recommend the use of ROVs specifically in order to reduce risks to human divers. Because there are often powerful tidal currents around the foundations of structures like wind turbine foundations, this can be a dangerous dive environment for humans. There is a great deal of general visual inspection work that needs to be done, but where an extremely close view is simply not required; the inspection needs to check the general condition of the pilings and caissons, for example. In this work, putting a human diver into the water isn’t necessary, as an ROV can provide the needed visual check.
(Primary source: http://www.bsee.gov/uploadedFiles/BSEE/Technology_and_Research/Technology_Assessment_Programs/Reports/700-799/747AA.pdf)