Methods of Small Hydropower Plants Connection in Water Supply System Martin Novak, Tomas Mozdren, Radomir Gono
Miroslava Gono
Department of Electrical Power Engineering VSB - Technical University of Ostrava Ostrava, Czech Republic
[email protected],
[email protected]
SmVaK Ostrava a.s. Ostrava, Czech Republic
[email protected]
Abstract—This paper deals with alternatives of connecting small hydropower plants (SHP) with water supply system. The requirements for plants with power output from 30 kW to 100 kW and more are outlined, the SHPs passportization in the city of Ostrava is described. The law amendments referring to the redistribution of state subsidy for renewable power energy sources are described.
where the hydropower is transformed to mechanical power. The shaft brings mechanical power to the generator which generates electrical power [7]. The principal parts of a SHP •
Barriers on water flows – weirs or dams which raise the water head and concentrate the flow into the penstock.
•
Penstock – concentrates the water flow into the water turbine. There are pressure and pressureless penstocks. The former are used mainly to drive raw water from reservoirs to water purification plants or to hydropower plants. Their specific cost is higher. Mostly they are steel pipes or reinforced concrete. Pressureless penstocks, such as raceways and channels are dug out and their cost depends on the length, cross slope, soil type and depending reinforcement of the channel walls. Both alternatives are often combined to achieve maximum head with minimum cost.
The priority for water supply companies is drinking water supply to a consumer. Some of these companies are able to use this water driven under pressure in water mains for power generation. Increase in building such small hydropower plants (SHPs) in water supply system has been supported by statesubsidized purchase price for power from RES. Installing a SHP in water supply system does not require long shut-downs; however, it is imperative that any pollution of drinking water is prevented. Operating a SHP brings substantial benefits and optimizes the quality of processed water by aeration during its passage through turbine. This helps blending of dosed agents with processed water. Water supply activities are highly power-consuming facilities, but the installation of SHPs can make the processing of drinking water self-sufficient in terms of energy, moreover excess power can be sold to public electricity network.
•
Screen – prevents large objects from flowing into the turbine.
•
Technical equipment – transmission, generator).
•
Tailrace – carries water back to the original bed.
Due to a lock of suitable areas for building SHPs, building SHPs on water mains reasonably employs unused heads in water supply systems.
Depending on water head SHPS are:
Keywords-water supply; small hydro power plants; connection to distribution network
I.
INTRODUCTION
The energy market covers testing, gaining, transforming, collection and transmission of energy to users. Industry, transport, construction, agriculture, municipal economy or households can be an energy recipient. Each country tries to seek to ensure energy security, allowing coverage of current and anticipated customer demand for fuel and energy in a technically and economically justified way, fulfilling the requirements of environmental protection [6].
II.
SMALL HYDROPOWER PLANTS
The principle of a SHP is in building a weir or a dam on the water flow. This concentrates the flow and raises the water head. Water is driven through the screen into the engine room
machine
set
(turbine,
SHPs are designed as [8]: •
Run-of-river – natural water flow in the profile is not affected.
•
Storage – water is stored in a reservoir or drawn off different sources.
•
Low-pressure – up to 20 m.
•
Medium-pressure – up to 100 m.
•
High-pressure – over 100 m.
Depending on the design SHPs are (Figure 1):
This work was supported by the Grant of SGS VŠB - Technical University of Ostrava (No. SP2014/187) and by the project ENET (No. CZ.1.05/2.1.00/03.0069).
978-1-4799-4660-0/14/$31.00 ©2014 IEEE
•
Weir
•
Derivative – before the water barrier a part of the water flow is driven into the derivative feeder SHPs, where the design head is used.
•
Dam – partially or fully enclosed in the body of the dam, at the foot of the dam or in a tower
Usually weir or derivative open plan is used.
Figure 2. SHP machine set [10].
The connection of a SHP to water supply systems that are regularly used can be the following.
Figure 1. SHP general arrangement [8].
Mostly Banki, Pelton, Francis or pump turbines are employed for SHPs. The amount of usable energy depends on the head (vertical change in elevation between the upstream and the tail stream water level) and flow (volume of water passing through turbines).
B. SHP on a water purification plant penstock A SHP Vyšní Lhoty, which was put in operation in 2008, can serve as an example. Specifically, this plant is installed on the penstock duct in the grit chamber of a water purification plant. The run-of-river plant has three pump machine sets working as turbines. The machine set comprises three asynchronous generators Siemens ETANORM 150-400 s P = 90 kW, ETANORM 200-400 s P = 110 kW and ETANORM 300-400 s P = 132 kW. Only one turbine is activated at a time and their control is fully automated, the inlet and outlet in turbines is controlled via hydro drive and electro-flaps. The operation regime is determined by the hydrological regime of the water flow and the raw water consumption. Figure 7. This connection is indicated as SHP No. 2 [10].
For using the energy of water flow it is necessary to create a vertical difference in elevations, which is achieved by building dams and weirs. A. Alternatives of connecting SHPs to water supply system The simplest connection of a machine set is an asynchronous generator and a properly adjusted pump working as a turbine. In Figure 2. there is a more complicated connection with more machine sets working in parallel. This connection is more suitable when flow parameters are fluctuating. The accurate pressure regulation is controlled by servo-valves [10]. Figure 3. SHP Vyšní Lhoty [10].
C. SHP on the water tower penstock • Water tower pressure penstock – Frýdek-Místek in 1997 is used as plant is run-of-river and has one asynchronous generator type
A SHP built in an example. The turbine and one MEZ Frenštát
F250MK06 at 37 kW. The turbine inlet is controlled with a flow valve via servo drive. The operation is fully automated [10].
Figure 4. SHP Frýdek-Místek [10].
•
Water tower pipe feeders – A SHP Hlavatce is located on their premises on a pressureless water tower pipe feeder. The machine set comprises an adjusted pump Sigma Hranice DE 400-LN-S. The flow rate is 500 l/s 8 hours a day. The pressure of 2.2 bar in the system is equal to the head of 2 m [3].
E. SHPs on water mains This type of a SHP is installed on the water grid mains directed to a subscriber. It can be located before the water tower (SHP No. 3) or a terrestrial water reservoir (SHP No. 4.), but also after them (SHP No. 5 and SHP No. 6) e.g. in a break pressure tank. Water towers are built in a level country and terrestrial water reservoirs on elevated ground. Their objectives are to secure water storage and necessary pressure in water mains and also to level the differences between the inflow from the water source and outflow to subscribers. Water is driven into a reservoir either by gravity (water source is higher than water reservoir) or by a force main (water source is lower than reservoir and water is driven in with a pump). The generator turbine is powered by the energy determined by two parameters - the head and the flow rate. Depending on these and other parameters, a suitable turbine is used. When the flow rate exceeds the specification of a turbine, a by-pass channel can be built to drive away the excess water. Another option is to build a pumped-storage SHP, as it provides a chance of accumulating the produced electrical power, and therefore to have another means of electrical power grid regulation. As an example we utilize a SHP Bílov (Figure 6.) located on a break pressure tank, built in 1988. The plant has one Banki-Cink turbine and an asynchronous generator type MEZ Frenštát 3AFP 355 S-8 at 132 kW. The inflow is regulated by a servo drive with a regulation segment of a turbine and the operation is fully automated [10].
Figure 5. SHP Hlavatce [3].
D. SHP on a dam Concerning the location of SHPs, these can be installed either under the dam barrier or directly in it. They are pumpedstorage plants that work in peak or semi-peak hours of daily load diagram. Their operators are not water supply companies as a rule, but the companies managing the dam, or the electricity companies with a river basin authority contract guaranteeing the operation of a SHP within their area. However, water supply companies can operate SHPs on dams as well, provided they have this kind of contract. This kind of connection is indicated in Figure 7 as SHP No. 1.
Figure 6. SHP Bílov [10].
Figure 7. Simplified scheme of SHP connection onto the water supply system.
III.
BASIC EQUIPMENT OF RENEWABLE ENERGY SOURCES PLANTS
The requirements for the basic equipment of renewable energy sources (RES) plants are stipulated in Regulations for Distribution System Operation. The electrical machines controlled from the dispatching are installed primarily due to limits in their production that were determined in Act 458/2000 Coll. In plants with power output from 30 kW to 100 kW a Ripple Control (RC) receiver will be installed for the above given reasons. In plants with power output of 100 kW and more, a RC receiver and a Remote Terminal Unit (RTU) will be installed [1]. A. Equipment of plants with 30 kW to 100 kW power output To disconnect the source from the distribution network, the dispatching will use a RC receiver controlled relay. In areas where RC signal cannot control disconnection, a RTU will be deployed. The active power will be regulated in steps from 0% to 100%. The RC receiver must be in operable mode even after the disconnection from parallel operation - therefore it must be powered from the distribution grid. The RC receiver for power output control cannot substitute the RC receiver for switching consumption tariffs.
modular cards which fit into corresponding units. The power processor of a unit, or in other words control system, processes input signals and output requirements, filters analogue and binary signals, and provides automation and protection. An auxiliary processor is used for control and signaling. Except for signaling of status DI and control with RC, measurement of alternation quantities, other events are monitored as well. These are - exceeding of temperature limits, power outages, faults in reading electrical quantities of voltage and current, and moreover, active power, apparent power, and reactive power quantities are calculated. Readings are taken every second and transmitted to the dispatching control system where they are stored for later use. Graphs can be generated to visualize a second-to-second or minute-to-minute sample readings. The dispatching control system is connected via data concentrators in dispatching centers with monitoring control systems and in electricity plants including RES. For data communication between dispatching control system and monitoring control systems, the protocols such as MDXL, HioCom2 are used, as well as other standardized protocols such as IEC 60870-5-101 and IEC 60870-5-104. The dispatching control system and data concentrators communicate with monitoring and control systems in Moravia region via the aforementioned IEC 60870-5-104 protocol [2].
B. Equipment of plants with power output at 100 kW and more The sources must be able to give rapid and accurate response to command sent form the dispatching. The active power regulation will be gradual from 0 to 30, 60 and 100%. The transmission of readings and signaling from the Remote Terminal Units must be provided for the distribution grid dispatcher. A dispatcher can specify a continuous voltage control and reactive power for an electrical power source. Remote control provides a standardized communication protocol via RTU communication interface. When RTU is owned by a distributor, the producer is to provide the power of 230V AC for powering the unit including internal recharging of the unit. However, when the unit is owned by the producer, the distributor is to provide an appropriate SIM card to secure communication with dispatching via the standardized communication protocol.
Figure 8. Remote Terminal Unit by Elvac a.s. [2]
There are various alternatives to the control systems interconnection. Either the deployment of protocols as a fixed point, or by using GSM (GPRS), in which case the RTU is to be equipped with plug-in modules enabling communication via appropriate protocols.
The specifications for RC receiver are identical with those in paragraph II. A. IV.
REQUIREMENTS FOR CONTROL DEVICES
The RES plant should be built near a source compatible with the terminal device in the dispatching center. In ČEZ Distribuce PLC, Moravia region almost all RES deploy RTU by Elvac a.s. These units not only used within and out of area controlled by ČEZ a.s., but they can located abroad as well. The RTU is a modular unit designed for data collection and control in distribution grids. It is easy to install and can be used for existing switchboards. The system itself consists of
Figure 9. Simplified scheme of communication between Remote Technical Unit and Dispatching Control System [1].
V.
LAW AMENDMENTS FOR RES SUBSIDY AFTER 2013
Since 1st January 2013 a new law 165/2012 Coll. is effective. This bill draws upon the EU legislature on the statesupported energy sources and it is a compromise with respect to the previously passed Czech National Renewable Energy Action Plan. The Act 310/2013 Coll. was passed in the third reading on 16th August 2013. This act substitutes the Act 165/2012 Coll. on state-supported energy sources. On 17th September 2013 the president signed this law amendment and it comes into force on 1st January, 2014. It comprises: •
•
•
Stop of support for the new power plants (except for plants employing wind, hydropower, geothermal energy or biomass that claimed the state support on or before 31st December 2012). From 1st January 2014 the state support is stopped for the RES plants in construction, except for those employing hydropower with installed capacity up to 10 MW (SHP). The state support is to be provided only to those licensed plants that will be put in operation before 31st December, 2015 or to plants with capacity up to 100 kW if the construction permit was granted before this law comes into force.
VI.
There are seven small hydropower plants (SHPs) in the area of the city of Ostrava in total. SHPs can be operated either isolated from the distribution grid or parallel with it. A combination of both modes is also possible when there is power surplus. Isolated operation is used by entrepreneurs with a hydropower source nearby their location who decided to be partially or fully self-sufficient in terms of energy by building a SHP. When a SHP works in parallel with the distribution grid, the power it produces is supplied to the grid. The combination of both operation modes is used by operators indicated in TABLE I. The operators in the corresponding location are obliged to buy out the energy from RES for the contract price stipulated by the Energy Regulation Office (ERO). However, due to a generous subsidy on purchasing price of RES energy, most SHP owners benefit more from selling all their produced power to the distribution grid and buy from it power for their own consumption. In the region of Moravia, the power from the SHPs indicated in TABLE I. is distributed to the grid 22 kV by ČEZ Distribuce. TABLE I.
Stop of state support for heat and power producers in joint-stock companies that have no registered shares issued or those with owners of foreign nationality who are unable to provide a statutory declaration with the names of the shareholders with shares of nominal value exceeding 10 % of the authorized capital of the producer, giving the source of this information. Supposed entering into force is 1st July 2014. Extension of solar tax – since 1st January 2014 power produced in solar power plants that were put in operation from 1st January 2010 to 31st December 2010 (excluding plants with installed capacity up to 30 kW) and received ‘purchasing price’ support is subject to 10 % tax (or 11 % in case of ‘green premium’ support).
•
Support stop for non-central production - the jointstock power producers who fail to meet transparency requirements on their corporate structure (see paragraph b) above).
•
Cover for power production costs - costs cover is shared by the customer, power plant operator and electrical grid and distribution grid operator. Maximum price is set by ERO on 495Kč/MWh [9].
State support stop excludes: •
high-efficiency cogeneration plants,
•
secondary energy sources,
•
heat produced with RES.
PASSPORTISATION OF SHPS
PASSPORTISATION OF SHPS IN OSTRAVA [3], [4], [5], [7] Pi [kW]
Wel [kWh]
MVE Hrabova
55
149.6
MVE Ostrava Vítkovice
220
1085.6
MVE Jez Lhotka
628
2349.4
2 x 100
240.6
55
-
49
-
30
-
Type
MVE Ostrava Odra MVE Vodojemy Muglinov MVE Ostrava Privoz I, II MVE Ostrava Privoz III
REFERENCES [1]
ČEZ, a.s.: Requirements for equipment for regulation and control of renewable energy sources connected to distribution system. [2] Elvac, a.s.: User's guide RTU7M [3] Atlas of the facilities using renewable energy sources [online], [cit. 2013-2-4], Available at: http://calla.ecn.cz/atlas/list.php?type=1 [4] Energy Regulation Office: Summary of given licences by ERO [online], [cit. 2013-2-4], Available at: http://licence.eru.cz [5] List of electricity producers from RES in 2011, [online], [cit. 2013-1016], Available at: http://www.eru.cz/user_data/files/Aplikace%20106/FAQIII/20130213_s eznam_OST_OZE_FINAL.pdf [6] W. Deluga, “Grupa Energetyczna Energa na krajowym rynku energii” Rocznik Ochrona ŚRodowiska, vol. 15 Numer 1, 2013. ISSN 1506218X. [7] P. Mastný, “Zdroje elektrické energie – vodní energie” [online], [cit.2014-2-5], Available at: http://www.ueen.feec.vutbr.cz/~mastny/vyuka/mmze/skripta/voda.pdf [8] J. Bouška, P. Knížek, J. Kašpar, “Sborník technických řešení MVE, Svaz podnikatelů pro využití energetických zdrojů,” Praha 2000. [9] Law 310/2013 Coll. - supported renewable energy sources. [10] M. Goňo, M. Kyncl, R. Goňo, “Renewable energy sources - new possibilities in using small hydropower stations,” Conf. EPE 2012, Brno University of Technology, 2012, vol. 1, pp. 657–659.
