The Swansea barrage (or the Tawe barrage) was completed in 1992 creating a new marina at the mouth of the River Tawe extending the leisure boat facilities already being offered by the old South Dock.[1]
The barrage structure includes a boat lock, spillway, fish pass and generatorturbine. The turbine serves a dual use: acting as a power generator for the National Grid as well as being used to pump water back into the Tawe river system. The barrage has an installed generating capacity of 200kW.[2]
The barrage scheme gave rise to a number of environmental concerns. Fish navigation up the river and dissolved oxygen levels were problems that arose after completion.[3] Salt water that came in at high spring tides sank to the bottom and stayed there, reducing oxygen levels. The Environmental Advice Centre was commissioned to undertake an aeration scheme trial in the River Tawe in the summer of 1998. The system was based on a diffuser design and propeller mixer, which proved highly effective at exporting the saltwater from the deep area of the trial site and raising dissolved oxygen concentrations at the bed.
Following the success of the trial system a more extensive system was designed for the river for installation in 1999 -2000. The first stage of the installation of the designed system was undertaken in June 1999 and comprised a combination of diffusers and a large propeller mixer.
The installation was conducted using a diving team to ensure optimal location of the diffusers within the river channel. The installation will be completed over two years to treat all the problem areas over a 4 kilometres (2.5mi) long reach of river and ameliorate the poor water quality presented in these areas.
Monitoring results from the system installed to date have indicated that aeration has effectively raised the oxygen concentration and assisted in the export of saline water from the system. Following the success of this work the Environmental Advice Centre is currently examining designs for other reaches of tidal river within the United Kingdom that display similar problems.
Following the success of the River Tawe aeration scheme the neighbouring Welsh city of Cardiff used the same method to improve the quality of the water in its newly created bay.
Other fears that arose with the building of the barrage such as the raising of the water table causing ground subsidence problems in the low-lying areas around the River Tawe. Since completion, no significant subsidence problems have arisen.
Cardiff Bay Barrage lies across the mouth of Cardiff Bay, Wales between Queen Alexandra Dock and Penarth Head. It was one of the largest civil engineering projects in Europe during construction in the 1990s.
Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods.
The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was developed in 1913 by Austrian professor Viktor Kaplan, who combined automatically adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over a wide range of flow and water level.
Micro hydro is a type of hydroelectric power that typically produces from 5 kW to 100 kW of electricity using the natural flow of water. Installations below 5 kW are called pico hydro. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks, particularly where net metering is offered. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without the purchase of fuel. Micro hydro systems complement solar PV power systems because in many areas water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum. Micro hydro is frequently accomplished with a pelton wheel for high head, low flow water supply. The installation is often just a small dammed pool, at the top of a waterfall, with several hundred feet of pipe leading to a small generator housing. In low head sites, generally water wheels and Archimedes' screws are used.
Water aeration is the process of increasing or maintaining the oxygen saturation of water in both natural and artificial environments. Aeration techniques are commonly used in pond, lake, and reservoir management to address low oxygen levels or algal blooms.
The Severn Barrage is any of a range of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. Ideas for damming or barraging the Severn estuary have existed since the 19th century. The building of such a barrage would constitute an engineering project comparable with some of the world's biggest. The purposes of such a project have typically been one or several of: transport links, flood protection, harbour creation, or tidal power generation. In recent decades it is the latter that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects. Following the Severn Tidal Power Feasibility Study (2008–10), the British government concluded that there was no strategic case for building a barrage but to continue to investigate emerging technologies. In June 2013 the Energy and Climate Change Select Committee published its findings after an eight-month study of the arguments for and against the Barrage. MPs said the case for the barrage was unproven. They were not convinced the economic case was strong enough and said the developer, Hafren Power, had failed to answer serious environmental and economic concerns.
Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid. Aeration processes create additional surface area in the mixture, allowing greater chemical or suspension reactions.
The Gorlov helical turbine (GHT) is a water turbine evolved from the Darrieus turbine design by altering it to have helical blades/foils. Water turbines take kinetic energy and translates it into electricity. It was patented in a series of patents from September 19, 1995 to July 3, 2001 and won 2001 ASME Thomas A. Edison. GHT was invented by Alexander M. Gorlov, professor of Northeastern University.
SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation. It was successfully decommissioned by SIMEC Atlantis Energy Limited in summer 2019, having exported 11.6GWh to the grid since 2008.
Marine Current Turbines Ltd (MCT), is a United Kingdom-based company which is developing tidal stream generators. It is owned by the German automation company, Siemens.
A water power engine includes prime movers driven by water and which may be classified under three categories:
Water pressure motors, having a piston and cylinder with inlet and outlet valves: their action is that analogous of a steam- or gas-engine with water as the working fluid – see water engine
Water wheels
Turbines, deriving their energy from high velocity jet of jets, or from water supplied under pressure and passing through the vanes of a runner which is thereby caused to rotate
Low-head hydropower refers to the development of hydroelectric power where the head is typically less than 20 metres, although precise definitions vary. Head is the vertical height measured between the hydro intake water level and the water level at the point of discharge. Using only a low head drop in a river or tidal flows to create electricity may provide a renewable energy source that will have a minimal impact on the environment. Since the generated power is a function of the head these systems are typically classed as small-scale hydropower, which have an installed capacity of less than 5MW.
A livewell is a water tank found on many fishing boats that is used to keep bait and caught fish alive. It works by pumping fresh water from the surrounding body into the tank, as well as keeping the water aerated. A rule of thumb for determining the necessitated size of a livewell is that every one inch length of fish needs a gallon of water if it is desired to keep the fish alive for a prolonged period of time.
A tidal farm is a group of multiple tidal stream generators assembled in the same location used for production of electric power, similar to that of a wind farm. The low-voltage powerlines from the individual units are then connected to a substation, where the voltage is stepped up with the use of a transformer for distribution through a high voltage transmission system.
The gravitation water vortex power plant is a type of micro hydro vortex turbine system which is capable of converting energy in a moving fluid to rotational energy using a low hydraulic head of 0.7–3 metres. This technology is based on a round basin with a central drain. Above the drain the water forms a stable line vortex which drives a water turbine.
A tidal stream generator, often referred to as a tidal energy converter (TEC), is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces.
Mogden Sewage Treatment Works is a sewage treatment plant in the Ivybridge section of Isleworth, West London, formerly known as Mogden. Built in 1931–36 by Middlesex County Council and now operated by Thames Water, it is the third largest sewage works in the United Kingdom. It treats the waste water from about 1.9 million people served by three main sewers serving more than the northwest quarter of Outer London and two further main sewers from the south and south-west. The plant has been extended and is constantly being upgraded with new process, most recently in OfWat Amp6 by the Costain Atkins Joint venture who delivered 6MW of Combined Heat and Power (CHP) generation, New process air blowers for Batteries A & B and six gravity sludge thickening streams. The site covers 55 hectares.
Tidal Lagoon Swansea Bay was a proposed tidal lagoon power plant that was to be constructed in Swansea Bay off the south coast of Wales, United Kingdom. Development consent was granted by the UK government in June 2015, and in June 2018 the Welsh Government approved the plan and offered to invest £200 million; however, later that month the UK government withdrew its support on value-for-money grounds. Other options to enable the proposal to go ahead were reportedly still being explored.
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