Showing posts with label wind energy. Show all posts
Showing posts with label wind energy. Show all posts

Monday, October 8, 2018

Smart Grids, the new power sector configuration







Smart Grids, the new power sector configuration
Introduction
A smart grid is an electrical grid which includes a variety of operational and energy measures including smart meters, smart appliances, renewable energy resources, and energy efficient resources  Electronic power conditioning and control of the production and distribution of electricity are important aspects of the smart grid. It is digital technology that allows for two-way communication between the utility and its customers, and the sensing along the transmission lines is what makes the grid smart. Like the Internet, the Smart Grid will consist of controls, computers, automation, and new technologies and equipment working together, but in this case, these technologies will work with the electrical grid to respond digitally to our quickly changing electric demand.
The basic concept of Smart Grid is to add monitoring, analysis, control, and communication capabilities to the national electrical delivery system to maximize the throughput of the system while reducing the energy consumption. The Smart Grid will allow utilities to move electricity around the system as efficiently and economically as possible. It will also allow the homeowner and business to use electricity as economically as possible. You may want to keep your house set at 75 degrees F in the summertime when prices are low, but you may be willing to increase your thermostat to 78 degrees F if prices are high. Similarly, you may want to dry your clothes for 5 cents per kilowatt-hour at 9:00 pm instead of 15 cents per kilowatt-hour at 2:00 pm in the afternoon. You will have the choice and flexibility to manage your electrical use while minimizing your costs.
Smart Grid builds on many of the technologies already used by electric utilities but adds communication and control capabilities that will optimize the operation of the entire electrical grid. Smart Grid is also positioned to take advantage of new technologies, such as plug-in hybrid electric vehicles, various forms of distributed generation, solar energy, smart metering, lighting management systems, distribution automation, and many more.
Traditionally, energy systems from power generation to homes are one-directional and based on more predictable, controllable and centralised power generation, Increasingly, more energy is being generated locally and connected directly to distribution networks, from solar panels on your roof, to small power plants. This is generally referred to by DSOs as distributed energy resources (DER) and in the specific case of renewables, distributed renewable energy sources (DRES).
The grid of yore is a one way transmission of energy; from power plant to transmission lines, substations and transformers to your home and to businesses. Plug in your smartphone and voilĂ  you have electricity. Through the 9,200 generating units and the 300,000 miles of transmission lines, the current grid's generating capacity is 1 million megawatts. While impressive, we have patched this antiquated system to the point where the underlying structure is no longer viable enough to meet the needs of the 21st century and beyond.
 A smart grid not only carries electricity from a power plant to the source of need, it also carries information to and from all points of interaction. Using the binary blessing of digital technology, two–way communication can be built into the grid to give utility companies moment to moment knowledge of electrical demand and disruptions. Using automation and computers as well as existing and emerging technologies and equipment, the smart grid will also make smart utility companies, smart homes, and smart businesses to augment the entire electrical exchange making efficiency the premier benefit of the smart grid.
Need
Energy systems are changing – fundamentally and fast. The importance of individual energy sources and options for power generation are changing, as are the ways in which electricity is transmitted and distributed. Power generation is becoming more and more decentralized making grid management increasingly complex. Electrical consumption continues to steadily rise all over the world.
Since the early 21st century, opportunities to take advantage of improvements in electronic communication technology to resolve the limitations and costs of the electrical grid have become apparent. Technological limitations on metering no longer force peak power prices to be averaged out and passed on to all consumers equally. In parallel, growing concerns over environmental damage from fossil-fired power stations has led to a desire to use large amounts of renewable energy. Dominant forms such as wind power and solar power are highly variable, and so the need for more sophisticated control systems became apparent, to facilitate the connection of sources to the otherwise highly controllable grid   Power from photovoltaic cells (and to a lesser extent wind turbines) has also, significantly, called into question the imperative for large, centralized power stations. The rapidly falling costs point to a major change from the centralized grid topology to one that is highly distributed, with power being both generated and consumed right at the limits of the grid. Finally, growing concern over terrorist attack in some countries has led to calls for a more robust energy grid that is less dependent on centralized power stations that were perceived to be potential attack targets.
Meeting these challenges requires cutting-edge products and services covering the entire energy value chain. Specifically, it calls for a comprehensive portfolio of physical and digital technologies, products and solutions that allow us to actively build our energy future. Continuous and expanded growth of the share of renewable in centralized and decentralized grids require an effective new approach to grid management, making full use of “smart grids” and “smart grid technologies”. According to a report of the International Renewable Energy Agency (IREA), there is a growing evidence in many countries that high levels of renewable energy penetration in the grid is technically and economically feasible, particularly as solar and wind technologies increasingly reach grid parity in economic terms.
Existing grid systems already incorporate elements of smart functionality, but this is mostly used to balance supply and demand. Smart grids incorporate information and communications technology in every aspect of electricity generation, delivery and consumption in order to minimize environmental impact, enhance markets, improve reliability and service and reduce costs and improve efficiency.
These technologies can be implemented at every level, from generation technologies to consumer appliances. As a result, smart grids can play a crucial role in the transition to a sustainable energy future in several ways: facilitating smooth integration of high shares of variable renewable; supporting the decentralized production of power; creating new business models through enhanced information flows, consumer engagement and improved system control; and providing flexibility on the demand side.

Benefits
·         Efficient transmission of electricity
·         Peak demand will be leveled off, which will help to reduce overall electrical rates
·         Integration of solar and wind power, micro–grids and large–scale systems will be included
·         Interruptions in electrical service can be recovered more quickly through rerouting
·         Increased security by improving native energy sources and making the grid less prone to disasters or attacks
·         Produces opportunity for new markets, products and services
·         The customer can   manage   electrical usage to save money
·         Smart meters are becoming more common and allow the customer  to see how much electricity is used and when and the cost of it simply by logging on to online account
·         Monthly statements may simply be a way of collecting money –  customers online account will be able to give  real time information about how and when the customer can change your power demands to reduce your costs
·         This is especially beneficial if  there is a  solar or wind system installed in the  home or business so the user  can regulate and even out demand to get the most from the renewable energy systems
·         Reduced operations and management costs for utilities, and ultimately lower power costs for consumers
·         Increased integration of large-scale renewable energy systems
·         Better integration of customer-owner power generation systems, including renewable energy systems
·         Improved security

Smart grids comprise a broad mix of technologies for modernizing electricity networks, extending from the end-user to the distribution and transmission levels.
Improved monitoring, control and automation technologies can help to enable new business models while unlocking system-wide benefits including reduced outages, improved response times, deferral of investment in the grids themselves and the integration of distributed energy resources.
At the end-user level, smart grids can enable demand flexibility and consumer participation in energy systems, including through demand response, electric vehicle charging and self-produced distributed generation and storage.
Demand flexibility can increase the overall capacity of the system to host variable renewable while accelerating the electrification of heating, cooling and industry at lower costs. Deploying a physical layer of smart grid infrastructure – underpinned by smart meters – can help to unlock these benefits.
Smart meter deployment has seen great strides in recent years in a few key regions  at the distribution level, “smartening” energy systems through information and communication technology (ICT) allows for optimization of grid monitoring and control. In particular, data and analytics allow for the real-time monitoring of conditions, opening up possibilities for predicting failures and carrying out remote maintenance.
Better and cheaper sensors are improving the visibility of grid conditions, allowing the physical capacity of the network to be increased. Overall, digital energy networks reduce the need to build new power lines or invest in physical network assets.
At the transmission level, new high voltage technologies allow for greater interconnection between networks and the connection of remote energy resources. Digital smart control technologies allow transmission networks to operate at higher capacities, closer to their physical limits. They can also improve management of interconnections between regions and countries.  
The Smart Grid represents an unprecedented opportunity to move the energy industry into a new era of reliability, availability, and efficiency that will contribute to our economic and environmental health. During the transition period, it will be critical to carry out testing, technology improvements, consumer education, development of standards and regulations, and information sharing between projects to ensure that the benefits we envision from the Smart Grid become a reality.  
Today, an electricity disruption such as a blackout can have a domino effect—a series of failures that can affect banking, communications, traffic, and security. This is a particular threat in the winter, when homeowners can be left without heat. A smarter grid will add resiliency to our electric power System and make it better prepared to address emergencies such as severe storms, earthquakes, large solar flares, and terrorist attacks. Because of its two-way interactive capacity, the Smart Grid will allow for automatic rerouting when equipment fails or outages occur. This will minimize outages and minimize the effects when they do happen. When a power outage occurs, Smart Grid technologies will detect and isolate the outages, containing them before they become large-scale blackouts. The new technologies will also help ensure that electricity recovery resumes quickly and strategically after an emergency—routing electricity to emergency services first, for example. In addition, the Smart Grid will take greater advantage of customer-owned power generators to produce power when it is not available from utilities. By combining these "distributed generation" resources, a community could keep its health center, police department, traffic lights, phone System, and grocery store operating during emergencies. In addition, the Smart Grid is a way to address an aging energy infrastructure that needs to be upgraded or replaced. It’s a way to address energy efficiency, to bring increased awareness to consumers about the connection between electricity use and the environment. And it’s a way to bring increased national security to our energy System—drawing on greater amounts of home-grown electricity that is more resistant to natural disasters and attack.
Giving Consumers Control
The Smart Grid is not just about utilities and technologies; it is about giving you the information and tools you need to make choices about your energy use. If you already manage activities such as personal banking from your home computer, imagine managing your electricity in a similar way. A smarter grid will enable an unprecedented level of consumer participation. For example, you will no longer have to wait for your monthly statement to know how much electricity you use. With a smarter grid, you can have a clear and timely picture of it. "Smart meters," and other mechanisms, will allow you to see how much electricity you use, when you use it, and its cost. Combined with real-time pricing, this will allow you to save money by using less power when electricity is most expensive. While the potential benefits of the Smart Grid are usually discussed in terms of economics, national security, and renewable energy goals, the Smart Grid has the potential to help you save money by helping you to manage your electricity use and choose the best times to purchase electricity. And you can save even more by generating your own power.

Description
Smart grid technologies are divided roughly into three groups:
1. Well-established: Some smart grid components, notably distribution automation and demand response, are well-established technologies that directly enable renewable and are usually cost-effective, even without taking into consideration the undeniable benefits of sustainability related to renewable energy integration.
2. Advanced: Smart inverters and renewable forecasting technologies are already used to increase the efficiency and productivity of renewable power generation, yet tend to entail additional costs. These devices start to help noticeably when capacity penetration for renewable reaches 15 percent or more (on any section of the grid) and become essential as this capacity penetration approaches 30 percent, although there is little downside to choosing smart inverters even at low penetration levels.
3. Emerging: Distributed storage and micro-grids are generally not “entry level” smart grid technologies and thus are less well-developed. Most utilities focus on other technologies first, except in special circumstances (such as with grant funding, high reliability requirements, or remote locations).
This shows that a range of enhanced smart grid technologies is already available to improve grid performance and enable higher penetration levels of renewable energy. Furthermore, the use of smart grids is cost-effective when installing new grids or upgrading old ones. Examples of cost-effective smart grid technologies include “smart meters”, which can measure and track the output of a rooftop photovoltaic (PV) system and send that data back to the utility operating the grid, and “smart transformers” that will automatically notify grid operators and technicians if the transformer’s internal temperature exceeds normal limits.

Applications of smart grid technologies can be found across the world, from isolated islands to very large integrated systems. For developed countries, smart grid technologies can be used to upgrade, modernize or extend old grid systems, while at the same time providing opportunities for new, innovative solutions to be implemented. For developing and emerging countries, smart grid technologies are essential to avoid lock-in of outdated energy infrastructure, to attract new investment streams, and create efficient and flexible grid systems that are able to accommodate rising electricity demand and a range of different power sources.
With renewable power shares sure to continue increasing, smart grid technologies in combination with appropriate supporting policies and regulations will be essential to transform the electricity system and create the grid infrastructure to support a sustainable energy future.

 Demand response support
Demand response support allows generators and loads to interact in an automated fashion in real time, coordinating demand to flatten spikes. Eliminating the fraction of demand that occurs in these spikes eliminates the cost of adding reserve generators, cuts wear and tear and extends the life of equipment, and allows users to cut their energy bills by telling low priority devices to use energy only when it is cheapest.[19]
Currently, power grid systems have varying degrees of communication within control systems for their high-value assets, such as in generating plants, transmission lines, substations and major energy users. In general information flows one way, from the users and the loads they control back to the utilities. The utilities attempt to meet the demand and succeed or fail to varying degrees (brownouts, rolling blackout, and uncontrolled blackout). The total amount of power demand by the users can have a very wide probability distribution which requires spare generating plants in standby mode to respond to the rapidly changing power usage. This one-way flow of information is expensive; the last 10% of generating capacity may be required as little as 1% of the time, and brownouts and outages can be costly to consumers. 
Platform for advanced services

As with other industries, use of robust two-way communications, advanced sensors, and distributed computing technology will improve the efficiency, reliability and safety of power delivery and use. It also opens up the potential for entirely new services or improvements on existing ones, such as fire monitoring and alarms that can shut off power, make phone calls to emergency services, etc.

Technology
The bulk of smart grid technologies are already used in other applications such as manufacturing and telecommunications and are being adapted for use in grid operations.
·         Integrated communications: Areas for improvement include: substation automation, demand response, distribution automation, supervisory control and data acquisition (SCADA), energy management systems, wireless mesh networks and other technologies, power-line carrier communications, and fiber-optics. Integrated communications will allow for real-time control, information and data exchange to optimize system reliability, asset utilization, and security.
·         Sensing and measurement: core duties are evaluating congestion and grid stability, monitoring equipment health, energy theft prevention,and control strategies support. Technologies include: advanced microprocessor meters (smart meter) and meter reading equipment, wide-area monitoring systems, dynamic line rating (typically based on online readings by Distributed temperature sensing combined with \ Real time thermal rating (RTTR) systems), electromagnetic signature measurement/analysis, time-of-use and real-time pricing tools, advanced switches and cables, backscatter radio technology, and Digital protective relays.
·         Smart meters.
·         Phasor measurement units. Many in the power systems engineering community believe that the Northeast blackout of 2003 could have been contained to a much smaller area if a wide area phasor measurement network had been in place.
·         Distributed power flow control: power flow control devices clamp onto existing transmission lines to control the flow of power within. Transmission lines enabled with such devices support greater use of renewable energy by providing more consistent, real-time control over how that energy is routed within the grid. This technology enables the grid to more effectively store intermittent energy from renewables for later use.
·         Smart power generation using advanced components: smart power generation is a concept of matching electricity generation with demand using multiple identical generators which can start, stop and operate efficiently at chosen load, independently of the others, making them suitable for base load and peakingpower generation.Matching supply and demand, called load balancing,is essential for a stable and reliable supply of electricity. Short-term deviations in the balance lead to frequency variations and a prolonged mismatch results in blackouts. Operators of power transmission systems are charged with the balancing task, matching the power output of all the generators to the load of their electrical grid. The load balancing task has become much more challenging as increasingly intermittent and variable generators such as wind turbines and solar cells are added to the grid, forcing other producers to adapt their output much more frequently than has been required in the past
·       Power system automation enables rapid diagnosis of and precise solutions to specific grid disruptions or outages. These technologies rely on and contribute to each of the other four key areas. Three technology categories for advanced control methods are: distributed intelligent agents (control systems), analytical tools (software algorithms and high-speed computers), and operational applications (SCADA, substation automation, demand response, etc.).  
The Future of the Smart Grid
  Industry, corporate & government money, and technology are pressing forward on building a Smart Grid. However, it isn't just the U.S. that needs to build a Smart Grid; this is a worldwide necessity. A report done by Memoori Business Intelligence Ltd,   found that Smart Grid equipment alone will require $2 trillion to "achieve full penetration of the world's existing grid . . to 2030"

Tuesday, September 11, 2018

Rooftop Wind Solutions




Rooftop Wind Solutions
 Introduction
Micro-wind turbines are used in micro-wind generation and are much smaller in scale than those used in conventional wind generation making them more suitable for residential energy production. Micro-wind generation is a method of micro generation that uses the flow of wind energy to produce electricity for a house or farm. Broadly speaking, there are two types of wind turbines that can be installed: vertical axis wind turbines and horizontal axis wind turbines.
The installation of a micro-wind turbine usually consists of the turbine and an inverter. Wind causes the blades of the wind turbine to rotate, generating mechanical energy. The mechanical energy from the rotation is converted to direct current (DC) in the turbine and using the inverter, is converted to alternating current (AC). The inverter output is connected to a breaker panel where the electricity can be shared among the electrical equipment in the home. Excess electricity can be exported from the home to the electrical grid using a bidirectional meter and credits will be provided accordingly by the retailer based on the electric current tariff for electricity.
The generation of electricity is mostly based on the rotational wind speeds of the wind turbines. Certain geographic locations are more suitable for producing electricity compared to others. Depending on the amount of wind that can be obtained from a region, the generation can vary. Another factor that can affect the performance of wind turbines is the obstructions in the area of the installed turbine. Obstructions from trees or other buildings will hinder the turbines from producing at its optimum capacity.
Rated Power
Wind turbines are advertised with a rated power. Small turbines, like those you’d see on a roof, are generally rated at 400W to 1kW.  The rated power of a turbine is a best-case scenario. It’s a measure of how much power the turbine will generate at the highest wind speed that the turbine can tolerate. To get a more accurate estimate, look at the turbine’s power curve. Here’s a typical power curve for a 1 kW turbine:


The curve shows that the turbine starts generating power at around 3 m/s (6.7 mph) - the cut-in speed. Slower winds don’t have enough power to make the rotor spin. As wind speed increases, there’s a rapid increase in power, but the power output only hits 1 kW (the rated output) when the wind speed is around 11 m/s (nearly 25 mph). To put that into perspective, if your land had average wind speeds of 25 mph, all of your trees would be permanently bent. It’s more likely that you’ll see winds in the 3 to 5 m/s range, which means that a 1 kW turbine is usually producing less than one-tenth of its rated value. The shut-down speed is the speed at which the turbine will apply a braking mechanism to prevent damage. A typical shut-down speed is just a few m/s higher than the rated speed, so the “sweet spot” - the range where the turbine produces its rated power - is pretty narrow.
Sustained Winds versus Turbulent Winds
To make wind power cost-effective, turbines need access to strong and sustained winds. A residential rooftop offers neither. Wind speed increases with altitude, and the top of a house is pretty close to ground level. Even worse, all the obstacles - trees, other buildings, even the house itself - cause turbulence in the wind. So instead of a fast steady breeze flowing in a mostly constant direction, you get short choppy gusts of wind coming from random directions. Turbulence not only decreases the turbine’s output, it also causes mechanical stress that shortens the turbine’s life. The rule of thumb is that the turbine should be at least 9 m (30 ft) higher than any obstacle within 150 m (500 ft): rooftop turbines should be mounted near the center of the roof rather than along the perimeter, because turbulence is greater around the outside of the roof than in the center. Fair enough, but that study only looked at turbulence, not overall production. Following its recommendations means that your turbine will last longer. That’s a good thing, because it could take a very long time for the turbine to generate enough electricity to offset the cost of the turbine itself. A better suggestion is to avoid putting wind turbines on the roof.
Payback Period
  A 400 watt horizontal axis wind turbine (HAWT)   with a 10 m (33 ft) tower, since higher altitudes are where you get the sustained winds, .with average wind speeds of 10 m is 3.6 m/s, or about 8 mph. With 3.6 m/s winds, the 400W turbine generates 50W. Assuming it runs 24/7/365, the turbine will generate 438 kwH per year. At a utility cost of  $0.12/kWh,  the turbine saves the owner $52/year in electricity cost. A typical 400W turbine costs about $400 - and that’s just the turbine, not the tower. The least expensive tower kit that I could find sells for just under $400, not including the concrete base. So at a minimum, it costs upwards of $800 for one of these turbines and its tower. That’s more than a 15 year payback period, which wouldn’t be terrible for a long-term investment, except that the turbine comes with a one-year warranty.  
What If the Grid Isn’t an Option?
It’s easy to say that these turbines aren’t worth the money when compared to grid power, but what about remote locations where grid power isn’t available? Let’s look at the 1 kW turbine and tower for $8800. We determined that it produces 675 kWh per year. Is there a better renewable source of energy? Solar?
In the same location, the average solar resource is 4.5 peak sun hours (PSH) per day, with a worst case of 2.6 PSH in the winter. To generate 675 kWh/year, a photovoltaic (PV) array would need to produce 1.85 kWh/day. In the winter, a 1 kW solar array would cover that, even if the overall system were only 75% efficient. (85% is a more realistic number.) A small PV system costs about $4/watt installed, so the total investment, including installation, is about $4000. Even better, the PV system has no moving parts so it requires no annual maintenance. PV seems the better option
Wind: Go Big or Don’t Bother
Wind power is a great source of renewable energy - at the utility scale. Large turbines are more efficient than small ones, and higher towers reach those energy-rich high speed winds. If you’re considering a small turbine, think again. Unless you’re in the Arctic region, you’re better off spending the money on solar panels.

Capacity Factor
The average capacity factor for rooftop wind turbines was 5%. This poor performance is currently a major factor limiting the feasibility of small urban wind turbines and is primarily due to inappropriate siting of the wind turbines. An urban environment contains turbulence caused by buildings and obstructions, and careful siting is required to avoid these less efficient winds. With proper siting, higher capacity factors can be achieved, making urban wind turbines more feasible. Capacity factors as high as 14% have been achieved in urban settings. Greater capacity factors are also possible considering that rural wind turbines see percentages in the 20-35% range and higher. These reasonable capacity factors provide a more assuring outlook for rooftop wind
Factors that inhabit Urban wind roof tops
The low capacity factor achieved in an urban environment is the main hindrance in rooftop wind turbine feasibility; however, it is not the only factor affecting it. The price of electricity and value of RECs also affect how much income is generated from energy produced with a wind turbine. These three factors have a significant impact on the economic feasibility of rooftop wind turbines. Using future projections for these factors, and   small increases in each of them could significantly reduce the payback period of rooftop wind turbines, making them more economically feasible.
Siting Factors
Certain areas and building types are more promising for rooftop wind turbines. Buildings that meet the following criteria would be easier and more effective to install rooftop wind turbines:  Above 150 feet tall, and taller than buildings upwind; Roof area of at least 5,000 square feet; Supported by columns to which the turbine can be mounted
 1 kW wall mounted wind turbine
Recently developed 1 kW turbines can be mounted on a wall and does not need a structure for mounting. 1000 W power while only 1.50 m in diameter and 15 kg in weight, An integrated dump load and braking system along with the following ;
·  2x patented aluminum rotor
·  Nacelle incl. wind direction following system
·  Grid inverter incl. on-board computer and display
·  Dump load incl. ceramic screws and mount
·  Automatic storm control system incl. sensor, actuator and relay
·  Protective wax coating for corrosive sites
·  Manual and detailed installation guide including pictures for each step
   The wind turbine can be plugged into the next wall socket. The new inverter will synchronize with your local grid. You start saving on your next electricity bill as soon as the wind starts blowing. The   inverter automatically adjusts to both 230 V and 110 V AC power. The energy generated directly feeds your appliances, only the missing power is bought from the grid. The power generation ability of the turbine is presented as follows:

The complete turbine ready for installation is priced at Euro 1400 (US $ 1620). This seems a more attractive solution which given better than average wind conditions could be feasible.

Why Micro Wind Turbines don’t work.
Size
A simple equation gives the power of the wind. Power = 0.5 x collection area x the wind speed cubed. What it tells us is that the power of a turbine is related to two factors: the size of the turbine and the strength of the wind.  The area of the circle is equal to the constant pi (3.14) times the radius of the circle squared. What that means is that as you increase the length of a turbine blade, the collection area increases disproportionately.  A micro turbine with Its blades 1.75m long, would give a collection area of just under 10sq m. Tiny. Small turbines have disproportionately smaller collection areas and therefore generate dramatically less power.
Wind speed
The key here is that cube function on the wind speed. The power of the wind is related to the cube of the wind speed. So, at low wind speeds you get virtually nothing. When it really blows it you get a lot of power. Double the wind speed and you get eight times the power. Quadruple it and you get 64 times as much. Eight times the speed and we're talking more than 500 times the power. Halve the wind speed to six meters per second (a moderate breeze) and - thanks to that cube law - you now get just 120 Watts - that's two standard incandescent light bulbs with average wind speeds likely to be between 4m and 5m per second the turbine would generate 25 Watts. That is barely enough for two energy saving light bulbs.  
Conclusion
Micro wind turbines are unable to generate significant amounts of electricity, at this point in time, to be financially feasible.  Wind solutions with small and micro turbines that are to be mounted on walls, will cost less than the mast mounted turbines but wall mounting will have disadvantages of lower wind speed. Work on micro turbines is still in progress and in the future we may have designs that are financially feasible. Small wind turbines in urban areas today are only profitable under very favorable conditions. The coupling of the small wind turbine to a storage system is crucial for cost-effectiveness.