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.
One of the most common uses for commercial underwater remote-operated vehicles (ROVs) is in conducting inspections of water tanks, ship hulls, and submerged infrastructure such as bridge components or dams. A critical element of these inspections is measuring the thickness of metal components like hulls or girders. How do ROVs conduct this type of measurement?
On the Aquabotix Endura line of high-performance commercial ROVs, we offer the Cygnus NDT Metal Thickness gauge as an optional accessory. These gauges use ultrasound technology to measure the thickness of metal objects underwater. By emitting an ultrasonic beam into the surface of the metal and analyzing the return sound, the Cygnus NDT can measure metal of thicknesses up to 10”, even through coatings such as paint up to 0.787” thick.
The Cygnus NDT is extremely easy to use. The included CygLink software allows the ROV operator to visualize the tool’s measurements remotely on the video feed. To make things even easier, the optional Cygnus Probe Handler automatically aligns the probe to the wall or item being measured, with 15 degrees of movement, even if the operator has not perfectly approached the measurement subject.
Tools like the Cygnus greatly enhance the utility of our Endura ROVs. As ROVs take on more responsible roles in things like underwater inspections, the need for tools such as the Cygnus will continue to grow.
There are almost 80,000 dams in the US Army Corps of Engineers National Inventory of Dams (NID), and that isn’t even a comprehensive list; the NID only covers dams which reach a minimum height and which hold back a minimum volume of water. There are many thousands of other dams, on private and government land, which are used for irrigation, flood control, aquaculture, drinking water, industrial use, and a myriad of other applications. Although most of these dams are extremely useful, they can also pose a serious danger to people and objects downstream of the dam. For obvious reasons, dam failure can have catastrophic consequences.
Accordingly, it is critically important that dams be inspected on a regular basis. The federal government, via the Federal Emergency Management Agency (FEMA), provides guidelines for inspections on dams under federal control. These guidelines suggest that dams should receive an informal “eyes-on” inspection as needed or following any significant incident at a dam (such as a flood, an earthquake, or vandalism), as well as a more thorough intermediate inspection of the dam and all related structures on an annual basis. Federal guidelines also suggest a formal full inspection of the dam be carried out at least every five years, with a full special inspection to be conducted when there is a major event such as a large flood or a major earthquake. Around 3,200 dams in the United States are owned outright by the federal government, and another 5,200 or so are not owned by the government but are located on government land. Although there are some complications about the regulation of those non-federally-owned dams, all told about 10% of the largest American dams fall under the federal guidelines.
The remainder of the dams in the United States are regulated by the state governments, with the notable exception of Alabama which leaves dams essentially unregulated. The state laws and regulations are a fairly diverse patchwork; some states require inspections to be paid for by the dam owners, while other states put that expense on the taxpayer. A few states like Texas do not have a formal inspection schedule at all (although inspections are strongly suggested) while most states have stringent schedules and extensive systems of classifications for which kinds of dams must be inspected and how often.
In general, however, in most places, dams are supposed to be inspected at intervals ranging from annually to every five years. The size of the dam’s impoundment (the volume of water the dam is holding back) and the population of the area in the dam’s potential flood area are the major factors determining how often and how stringent such inspections must be. Again depending on the location, inspections can be carried out by divers or by surface inspection, usually with at least some underwater work being required. Clearly, there is an astonishingly large amount of inspection work called for in the dam safety regulations.
ROVs play a major role in accomplishing the difficult task of inspecting dams while leaving them in service. Many dams are simply not able to be “turned off” so that an inspection can take place. Even when dams are equipped with the ability to dewater areas for inspection or repair, such dewatering is time-consuming and expensive. ROVs and human divers are able to work in areas of the dam without having to go through the dewatering process, saving large amounts of money.
One area where ROVs have saved enormous sums for dam owners is in assessing the need for cleaning of trashracks, reservoirs, and head ponds. Rather than adhering to a calendar schedule for the dredging of such ancillary dam components, an ROV inspection using sonar can inexpensively check whether an area needs to be dredged at all.
Of even more importance than saving money is saving lives. At many dams, particularly hydropower dams, there are areas where it is very dangerous for a human diver to enter the water. High water flows and high pressure differentials can be life-threatening conditions. The use of an ROV allows dive teams to conduct preliminary safety assessments, measuring flow, depth, and water temperature before ever putting a human being into the water. ROVs have also been used to check safety concerns such as the open or closed status of a head gate, where a gap of a few inches in a nominally “closed” gate could pose a lethal risk to a diver in the area.
At large dams with deep water areas, ROVs have the ability to work deeper than human divers without needing mixed-gas equipment. (Divers going below 30 meters require decompression tanks and other specialized equipment that make a dive more expensive.) By using divers for shallow work at a dam, and ROVs for the deeper dives, a cleaning or inspection process can be accomplished at much less expense. In addition, ROVs can conduct survey work using tools such as multibeam sonar more efficiently than human dive teams. As dam infrastructure ages, inspections of components like downstream draft tube slabs require a great deal of precise surveying work to assess the condition of the slab.
As in many other areas of underwater work, ROVs are capable of making a large contribution to the jobs being done by human divers. ROVs make underwater work safer, more effective, and less expensive.
Check out the HydroView Pro inspecting a separation tank. The walls, pipes and sediment levels were observed. Pay close attention to the end of the video where the bottom skids of the HydroView were used to evaluate the depth of the sediment - just another example of an innovative way to use an ROV.
Thermal stratification in potable water storage tanks poses risks for system operators and their customers. Water treated with chlorine or chloramines generally remains stable for a few days. Thermal stratification can hamper passive mixing or cycling of the water resulting in the potential for limit aging or deterioration of the disinfectant chemicals. Drops in residual chlorine can lead to growth of bacteria often requiring the draining and flushing of the tank.
Thermal stratification can also promote the formation of nitrates and other disinfection byproducts, allow for the formation of ice endangering coatings and tank walls and allow headspace temperatures to rise above recommended levels.
The HydroView Pro 5MWI is equipped with depth and temperature sensors. Data from these sensors is recorded during tank inspections and downloaded following the inspection in an easy to read/report format. Additional water chemistry sensors are available and can be integrated with the vehicle and the data reporting module.