Tower Cost Research Articles

Strategy for mitigating wake interference between offshore vertical-axis wind turbines: Evaluation of vertically staggered arrangement

Wake interference between wind turbines potentially decreases the power output of offshore wind farms. While the staggered arrangement shows promise for mitigating this interference, the understanding of the impact of vertically staggered setup remains ambiguous, especially in the case of vertical-axis wind turbines (VAWTs). Also, the difference between horizontally and vertically staggered arrangements needs to be clarified. This study aims to shed light on these ambiguities, systematically evaluating the effectiveness of vertically staggered arrangement in mitigating wake interference between offshore VAWTs. High-fidelity computational fluid dynamics simulations are used to investigate the wake interference between two vertically staggered MW-class VAWTs. Typical separation distances (3D ≤ LS ≤ 7D) and different vertically staggered distances (−0.25H ≤ LV ≤ 0.75H) are considered, where D and H denote the turbine diameter and blade span length, respectively. Employing the Taguchi method, the effectiveness of horizontally and vertically staggered arrangements is compared, and the relatively optimal layout of the turbine array is identified. The results show that the vertically staggered arrangement significantly improves the power performance of the downstream turbine, e.g., the power output increases by 75.96% when LS = 7D and LV = 0.25H. When dealing with smaller LS (e.g., 3D), a negative LV is suggested, which reduces the tower cost while preserving the performance improvement. The vertically staggered arrangement has a greater impact on wake interference than the horizontally staggered arrangement. In terms of the relatively optimal layout, the power output of the turbine array is increased by 46.27%. These findings would contribute to the layout design of offshore wind farms.

Research of Turbine Tower Optimization Based on Criterion Method

Tower cost makes up an important part in the whole wind turbine construction especially for offshore wind farms. The main method to reduce tower cost is to reduce tower weight by optimum design. This paper proposes a two-level optimization criterion method for the optimal design of steel conical tower considering different structural reliability and uncertainty, along with the discreteness of design variables such as tower thickness and bolt type. In the first level, the tower shell geometry can be obtained by section design method; in the second level, bolted connections and flanges are designed based on the results of the first level. Then, summarized analysis and iterative calculation is performed to obtain optimum tower design with constant strength and rigidness. This method will play an important role in offshore customized turbine design.

Impact of the ground clearance on the annual energy production and tower cost of an offshore wind turbine

This article analyzes the impact of the ground clearance on the Annual Energy Production (AEP) and tower cost of a 20 MW offshore wind turbine. In addition, the influence of the rated wind speed on the analysis result will be considered. The AEP is computed by considering wind speed variation over the swept area of the rotor blades. The tapered tubular steel tower is considered for mass and cost calculation. The tower is considered as a fixed-free cantilever beam with concentrated mass at the free end. The analysis shows that the ground clearance only has a minor impact on the AEP but it has a remarkable impact on the tower mass. Specifically, when the ground clearance reaches 50 meters, the AEP only increases by roughly 3% while tower mass is nearly doubled compared to the case with no ground clearance. The results also reveal the significant impact of the rated speed on both the AEP and tower mass.

A centrally heated, air-coupled adsorption cooling system driven by waste heat

• Centrally heated, externally cooled adsorbent bed design presented. • Small-scale adsorption chiller with cooling duty < 100 W demonstrated. • COP of up to 0.1 and SCC of 4-80 W kg -1 predicted and experimentally demonstrated. A novel centrally heated, externally cooled (CHEC) adsorbent bed is conceptualized, modeled, and tested at a lab scale. It eliminates the need for cooling liquid lines and controls to the adsorbent bed, reducing system complexity and allowing the system to be used over a large range of thermal inputs. The reduction in complexity is achieved by using the external surface of the bed to directly transfer heat to the surrounding air. Such a system is ideal for small-scale waste heat utilization where a chiller tower cost or space prohibitive. The activated-carbon/ammonia working pair is chosen and system performance modeled over a range of waste heat temperatures. Coefficients of performance (COP) of up to 0.1 and Specific Cooling Capacities (SCC) of 4-80 W kg -1 are predicted and demonstrated experimentally for small-scale systems delivering 100 watts of cooling or less. Performance is expected to improve dramatically at larger system scales due to the larger bed-to-auxiliary thermal mass ratios. This concept trades system efficiency for reduced system complexity. It should also improve system reliability and reduce system cost by eliminating valves and pumps required for the cooling system.

Research on Single Tower Cost Prediction Technology of Transmission Line Engineering Based on 3D Design

Overhead transmission line project investment and construction is an important part of the daily investment activities of power grid companies. With the continuous advancement and implementation of my country’s power system reform, improving the efficiency and efficiency of investment in power grid projects has become the main way for grid companies to invest. The construction and development of overhead line projects is an important support for power grid companies to ensure the safe and stable supply of electricity. The construction cost control of large-scale overhead line projects faces many influencing factors. Factors such as terrain, geology, meteorology, and transportation conditions will cause large differences in cost and other realities. Therefore, strengthen the lean management of the construction cost determination of overhead line projects, rely on the development and application of three-dimensional design, strengthen the construction of a “tower-oriented” construction cost determination system, reasonably control project investment, and increase the level of power grid construction investment efficiency.

Research on Forecasting Technology of Single Base Tower Cost in Transmission Line Engineering

For a long time, the overhead transmission line project budget, completion settlement and financial final accounts are all valued according to the entire line. The project construction management and asset collection have not yet been refined. The management is not separately calculated according to the actual investment of different towers, and cannot be reflected in each base tower. The actual cost level and the accuracy of the cost need to be further improved. Therefore, this paper combines the actual pain points and difficulties of overhead line engineering cost management, and innovatively builds a pricing model based on a single base tower. When the company strengthens the construction drawing budget management, improves the project settlement level, accurately controls risks, and realizes high-quality management of cost management. The level of leanness is of great practical significance.

Optimization of composite material tower for offshore wind turbine structures

The focus of this study was to investigate the application of lightweight fiber reinforced composite materials in the construction of offshore wind turbine support structures. A composite tower design suitable for the NREL 5 MW reference wind turbine is presented. The design is based on the most automated and low cost composite manufacturing methods (pultrusion and filament winding) and the conclusions of this study may not be applicable for offshore structures using different composite material construction techniques. The mass of the tower was minimized using gradient based optimization approach. The cost of a composite tower was calculated and levelized cost of energy (LCOE) projections are discussed in comparison with the existing steel tower cost. The study determined that while the composite tower is technically feasible and has a lower mass than a comparable steel tower, uncertainty remains in how it compares economically in terms of LCOE.

Dynamics and optimal control of flexible solar updraft towers

The use of solar chimneys for energy production was suggested more than 100 years ago. Unfortunately, this technology has not been realized on a commercial scale, in large part due to the high cost of erecting tall towers using traditional methods of construction. Recent works have suggested a radical decrease in tower cost by using an inflatable self-supported tower consisting of stacked toroidal bladders. While the statics deflections of such towers under constant wind have been investigated before, the key for further development of this technology lies in the analysis of dynamics, which is the main point of this paper. Using Lagrangian reduction by symmetry, we develop a fully three-dimensional theory of motion for such towers and study the tower's stability and dynamics. Next, we derive a geometric theory of optimal control for the tower dynamics using variable pressure inside the bladders and perform detailed analytical and numerical studies of the control in two dimensions. Finally, we report on the results of experiments demonstrating the remarkable stability of the tower in real-life conditions, showing good agreement with theoretical results.

A review of offshore wind turbine nacelle: Technical challenges, and research and developmental trends

The turbine nacelle with traditional wind power generation system is heavy, especially in offshore applications due to the large mass of the power frequency step-up-transformer operated at 50 or 60 Hz, and copper conductor generator. For example, the weight and volume of a 0.69/33 kV 2.6 MVA transformer are typically in the range of 6–8 t and 5–9 m 3 , respectively. The weight for a 10 MW direct drive permanent magnet generator is about 300 t. These penalties significantly increase the tower construction, and turbine installation and maintenance costs. The tower cost represents 26% of the total component cost of the turbine and on average about 20% of the capital costs are associated with installation. Typical maintenance cost of an offshore wind turbine is about 2.3 cents/kWh, which is 20% higher than that of an onshore based turbine. As alternative approaches to achieve a compact and lightweight offshore wind turbine nacelle, different concepts have been proposed in recent years, such as step-up-transformer-less system, medium-frequency (in the range of a few kHz to MHz) power transformer-based system, multilevel and modular matrix converter-based system and superconducting generator-based system. This paper aims to review the technical challenges, current research and developmental trends, and possible future directions of the research to reduce the weight and volume of the nacelle. In addition, a comprehensive review of traditional wind power generation technologies is conducted in this article as well.

Towards Holistic Power Tower System Optimization

Many stakeholders today consider power tower systems to be the most promising CSP technology for the future. Therefore much effort is spent to improve individual components and subsystems. While these are valuable steps towards cost reduction, it is also of great importance to perform an overall, i.e. ‘holistic’, system layout and optimization process. Still, even today heliostats are often characterized and even compared using the single parameter ‘cost per square meter’, which is not sufficient. More factors like optical and tracking accuracy, shape, structural deformation under operation loads and maybe even power consumption have to be factored in to allow for a meaningful comparison.In the paper recent activities targeting at a more holistic power tower system optimization are described. For the overall layout process of heliostat field, tower and receiver the complete system is modeled using SAM or an in-house tool based on SolTrace and Matlab to determine investment cost, annual electricity generation and resulting levelised electricity costs. By doing so, different heliostat types and field layouts can be directly compared using LCoE as a reasonable figure of merit.This logical approach to identify the optimum heliostat design is described and illustrated using two generic heliostat designs and the respective field layouts as an example; a recently developed updated tower cost curve is used. It is found that using specific heliostat costs (i.e. $/m2) alone as a figure of merit to assess different heliostat designs can be misleading, because heliostats characterized by lower specific investment costs, but also lower optical and tracking accuracy, can lead to higher levelised electricity costs, which means the real objective of power plant optimization is not reached by looking at heliostat costs per square meter alone.

Symbol for a City

Compared to a butterfly, Shenyang, China's Sanhao Bridge serves as a new landmark for a city transforming itself. Despite its eye catching design, Sanhao Bridge's real innovation is its efficient load carrying system, which combines girder and cable-stayed bridge capacities. The bridge, one of nine spanning the Hwun River, has a total of six lanes, with paths for pedestrians and bicycles on either side of the deck. Bridge planning and design are discussed by the author, and include challenges such as assembling the tower, whose leaves were prefabricated in sections, as well as employing a concrete girder without significantly increasing tower cost.

Electricity generation using wind energy conversion systems in the area of Western Greece

Abstract Weibull parameters estimated by three different methods at four weather stations in the area of central Western Greece were used to estimate wind power potential in this area. A linear correlation was observed between the above mentioned parameters and the measured mean wind speed values. Additionally, analysis of the “unit energy cost”, being the specific cost per kilowatt hour, obtained for several wind turbines at different hub heights has been conducted for every station. Our analysis demonstrated that it is possible to profit from electricity generation in Missolonghi and Aktio, especially if larger wind turbines are to be used. The specific cost per kW h decreases as wind turbine size increases for comparable systems made by the same manufacturer with similar performance but with different rated power (size). The observed correlation between these parameters is hyperbolic with the greater decreasing rate in the less windy sites. Moreover, the cost per kilowatt hour increases with hub height due to the increasing tower cost.

Economic feasibility of photovoltaic systems in the developing countries

The economic feasibility of both photovoltaic (PV) stand alone and grid connected systems have been studied taking into account the prices of PV components in 1984 dollars. For stand alone PV systems, a comparative economic analysis with diesel generators is given. Different types of loads to be supplied by the stand alone PV or diesel systems are considered. Each load type is characterised by the ratio between energy demand during day time to that during a complete day. This ratio is denoted by “load factor”. The load factor plays a major role in determining both array and storage size. A fixed array tilted at an appropriate angle is considered for stand alone systems to minimize maintenance and operating costs for applications likely to be in remote areas where no technician is available. The impact of power availability on PV system cost has been thoroughly investigated herein. For PV grid connected central power plant a rather sophisticated, elaborate and efficient tracking system is considered to minimize the overall cost of 1 kWh produced by the power plant. The major factor in grid connected systems is how much oil can be saved by installing such a power plant so that a developing country government can export more oil (or decrease their oil import) to improve its balance of payment. The advantages of large scale PV grid connected systems are: (1) no storage batteries are needed and (2) prices of PV modules drastically drop when large systems (MW range) are required. An extremely important factor for a large scale PV grid connected power plant is that about 50% of the overall cost can be paid in local currency. Such costs are installation cost, labour cost, wiring cost, power tower cost, tracking motors cost,…etc.

Analysis of Heat Transfer Surface Geometries for Dry Cooling Tower Applications

An analysis of heat exchanger surface geometries for the purpose of reducing dry cooling tower cost is presented. Two sets of results are derived. The first set can be used to evaluate heat transfer surface geometries in an attempt to select those most suitable for dry cooling tower applications. The second set of results can be used to direct research and development efforts toward developing better geometries for dry cooling tower applications. The first set of results is general and is applicable to all heat exchanger surface geometries. The second set is valid only for helical round or continuous fins having smooth, serrated, or cut fins and for staggered and in-line tube arrangements. The methods developed in this paper are not restricted to dry cooling towers per se, but are valid for other applications of fin tube heat exchangers as well.

Waste Heat Disposal to Air with Mechanical and Natural Draft—Some Analytical Design Considerations

There is a growing acceptance of the future necessity of dry and wet/dry cooling tower systems for large power stations in spite of their economic penalty compared with once-through cooling, cooling ponds, and evaporative cooling towers. If technological improvements succeed in reducing the current costs of dry cooling towers, their future applications will be accelerated. The main objective of this work is to quantify the factors that reduce the overall size and cost of the tower and the associated heat transfer system and to provide a basis for establishing the conditions that result in dry cooling tower cost reductions. As a first-step, the design equations for forced-and natural-draft dry cooling towers are derived in close form to give explicit relations for salient design variables. Subsequently, these equations are used to establish a set of influence coefficients for quantifying the effects of various key design variables on the design of forced- and natural-draft cooling towers.

Cooling Water Sources for Power Generation

In this paper a forecast of thermal discharge growth by type of generation is derived from a forecast of electric generation, an estimate of generation mix, and the expected heat rates for each type of plant. Alternate methods of heat dissipation are explained and economically evaluated in terms of incremental costs additions to a base generation cost for once-through fresh water cooling. Generation cost increases are shown to be less than 5% for each type of cooling except for nonevaporative dry cooling. A survey of plant locations which includes a cost comparison of supplemental cooling at the load center versus power transmission from a once-through cooling water source indicates that approximately 70% of future generating stations will require supplemental cooling systems. Two cases of cooling tower cost optimization performed on a specific plant demonstrate how significant savings on a present worth basis can be obtained when more sophisticated analytical techniques are applied.

A Consideration of the Radio-Frequency Voltages Encountered by the Insulating Material of Broadcast Tower Antennas

A knowledge of the radio-frequency voltages on the insulation of broadcast tower antennas is important to the design engineer, since a too-large factor of safety may add unduly to the tower cost. Attention is first given to the base-insulator voltage. The magnitude of this voltage is also of interest in the design of lighting chokes and coupling equipment. Theoretical values are derived and shown in curveform as a function of antenna height. The theoretical curves are supplemented by experimental data taken on self-supporting tapered towers, guyed cantilever towers, guyed uniform-cross-section towers, and guyed tubular steel masts. A theoretical treatment is then given concerning the role of guy wires from an electrical standpoint. Consideration is given to the currents in the guys, and the voltages on the guy insulators. Measurements are presented of the voltages existing on the guy insulators of two guyed masts of different constructions. These voltages are found to be so small that there seems little need for elaborate insulation except for the presence of high static or induced lightning voltages. The paper is concluded by some considerations of ways of providing protection against these high instantaneous and random voltages without the use of expensive and elaborate insulation.