Analytical performance and economic evaluation of residential wind or wind and solar powered heating systems

A performance and cost model for a variety of wind powered space and water heating systems for single family residences is presented. In addition to wind powered systems, combined wind and solar systems are modeled and compared to conventional and solar only heating systems. Analytical results are presented for a site in Amherst, Massachusetts. System capital economic details include an itemized cost breakdown of the wind heating system components. The results demonstrate that wind powered systems are presently competitive with electric based heating systems and will be competitive with oil or gas systems in the future.     

A design procedure for wind powered heating systems

This paper presents a generalized design procedure for the month-by-month prediction of performance of wind powered residential heating systems. In its initial form, the technique is restricted to the simulation of residential heating systems using conventional horizontal axis wind turbines that dissipate their output into water based thermal storage systems (via electrical resistance heaters or fluid dissipation devices). The procedure using a graphical formulation (Wf-chart) is designed to give the monthly heating energy fraction supplied by a wind heating system with a minimum of site, wind turbine, and system input parameters. Such information is useful for simple performance studies or as input for economic assesment of wind heating systems. In addition example results of the calculational procedure for a typical wind heating system are presented.     

Wind power systems for zero net energy housing in the United States

This work investigates the feasibility of renewable energy housing development in the U.S. using wind power and solar thermal systems to attain zero net energy consumption. The over all objective was to determine how the wind power and solar thermal system designs and economics differ with various climates, wind and solar resources, energy prices, and state incentives, such as net-metering. Five U.S. cities, one in each of the five climate zones, were selected for this study based on their potential for wind power. A zero net energy housing design tool was developed in order to analyze and compare various system designs. The energy performance and economics of the designs were compared for various sizes of housing development, for seven turbine models, and selected heating systems. The results suggest that while there are some economical options for wind powered zero net energy housing developments, they are generally more expensive (except in the warmest climate zone) than housing with natural gas heating. In all of the cases, the economies of scale for large-scale wind turbines gave more of an economic advantage than net-metering programs gave small- and medium-scale wind turbines.     

An analytical study of a hybrid wind-passive solar system

This paper presents the results of an analytical performance and economic evaluation of a combined passive solar and wind powered residential heating and electrical energy system. Simulated in a New England wind and weather environment, the modeled system is based on the coupling of a vertical axis wind turbine with a super-insulated passive solar house. The analytical model is composed of four major sections: (1) residential heating and energy load; (2) wind turbine generator system; (3) energy system performance model; and (4) life-cycle costing economic analysis. Results for the heating, electrical supply and economic performance of the system are presented, varying such key parameters as residence window area, insulation, storage size, wind turbine size, and site average wind speed. These results show that when sited in adequate wind regimes (average wind speed greater than 5.4 m/sec (12 mph)) and coupled with super-insulated passive structures, wind turbines can provide significant fractions of the electrical and heating requirements in the New England environment.     

Cost of house heating with solar energy

There has long been a need for a practical method of predicting the true cost of heating a house with solar energy and designing the heating system (solar and auxiliary) to achieve the minimum total annual heating cost possible under the particular climatic, geographic, and residential characteristics involved. Rough approximations based on various types of averaged values of weather and seasonal variables have previously been developed, but the reliability of such methods and results is open to question. The authors have therefore made a rigorous analysis of projected solar heating costs in eight U.S. cities and have optimized the heating system design in each location.The analysis involved the use of a high speed computer and approximately 400,000 hourly observations in eight cities of radiation, temperature, wind, solar altitude, cloud cover, and humidity. Equations for performance of flat plate solar collectors and sensible heat storage systems were developed and programmed with the above weather variables and with eight design parameters comprising house size, collector size, storage size, collector tilt, number of transparent surfaces in collector, hot water demand, insulation on storage unit, and thermal capacity of collector. Capital and operating costs were quantitatively related to heating system design parameters, and the values of all design variables which yielded lowest annual heating cost in each city were then selected.The findings are presented in the form of two tables and ten graphs, showing heating costs as functions of various design and location factors. The relative importance of each factor is discussed, and the overall costs of solar heating are compared with the costs of conventional heat supply in each location. The method for designing the least-cost combination of solar and conventional heat supplies is also shown, and an example of the use of the method is presented.     

自然循环平板式太阳能热水系统的设计计算

提出了一种自然循环平板式太阳能热水系统水流阻力的工程计算方法，对采用不同管径循环管，由1－10架铜铝复合和铝翼管集热器单排并联组成的自然循环系统,进行了水流阻力核算。并根据水流阻力核算结果，对较大集热面积自然循环平板式太阳能热水系统的设计进行了分析与讨论。     

Design and performance of large low-cost solar water heating systems

An analysis is presented for the monthly performance evaluation of a simple design low cost solar water heating systems. A sample of typical results is presented which confirms their suitability as solar heating systems for summer peacking or as solar preheaters for year around loads.     

Simulation and cost optimization of solar heating of buildings in adverse solar regions

In the present study a model has been developed which simulates the effects of hourly weather conditions on the performance and cost of a combined solar/conventional heating system for buildings in cold, cloudy climates. The model exhibits the effects of several system and cost parameters on combined system cost so that optimal designs can be determined.Performance and cost results are presented for 1971 Ottawa, Ontario, weather data. The economic analysis, which treats both collector and conventional system fuel costs parametrically, shows that solar heating of a typical house in cold, cloudy climates is economically competitive with fuel oil heating only if the price of oil rises to approximately 80¢/gal.     

Economic evaluation and optimization of solar heating systems

A procedure is developed for assessing the economic viability of a solar heating system in terms of the life cycle savings of a solar heating system over a conventional heating system. The life cycle savings is expressed in a generalized formby introducing two economic parameters, P₁ and P₂, which relate all life cycle cost considerations to the first year fuel cost or the initial solar system investment cost. Using the generalized life cycle savings equation, a method is developed for calculating the solar heating system design which maximizes the life cycle savings. A similar method is developed for determining the set of economic conditions at which the optimal solar heating system design is just competitive with the conventional heating system. The results of these optimization methods can be presented in tabular or graphical form. The sensitivity of the economic evaluation and optimization calculations to uncertainties in constituent thermal and economic variables is also investigated.     

Passive and active residential solar heating: A comparative economic analysis of select designs

This paper compares four passive solar heating concepts to a conventional air collector/rock storage system. Masonry (Trombe) and water walls are considered in the presence and absence of night insulation. The performance of optimally sized systems is evaluated on a state-by-state basis. The effects of low interest loans and National Energy Act (NBA) income tax credits are examined. With natural gas as the alternative fuel, the passive designs evaluated here offer more promise than the active system. This is true with or without inclusion of incentives, although either incentive option enhances economic performance. The passive designs evaluated in this paper are economically competitive against the electric resistance alternative in all but a few states. Moreover, on a life cycle cost basis, these designs are feasible today. Although the optimal solar fractions are generally low, passive designs offer the opportunity to incorporate solar heating into a new home at costs much less than their active counterparts. This is because there are no discernible fixed costs, thereby allowing a simple movement from zero to 100% solar when evaluating economic feasibility. When both active and passive design are shown to be cost competitive against alternative fuels, higher solar fractions will be associated with the active systems. This is principally due to the substantial fixed cost component of active systems, which forces one to achieve a given solar fraction before economic feasibility can be shown.     

On optimal zone heating and energy conservation in passive solar buildings

Strategies for reducing the energy consumption of buildings include energy conservation, passive solar, and zone heating systems. In this paper, the constrained and global interzonal and overall building load coefficients, and the optimal mix of energy conservation, passive solar and zone heating are calculated as a function of economic and thermal parameters. Results are presented for the sensitivities of the optimal cost fractions to changes in the cost of passive solar and zone heating. For representative costs, the analysis indicated the largest component is energy conservation, followed by passive solar, zone heating and interzonal insulation.     

The nonconvecting solar pond applied to building and process heating

Recent studies indicate that solar pond house heating systems could be competitive with some conventional ones, particularly if a pond were to be used to supply thermal energy to several buildings. It is appropriate and important, therefore, to extend these investigations to include industrial process heating and also the influence of variations in salt content and unit price of salt on pond cost. To do this, equations are derived which yield a single set of dimensions for a hypothetical pond satisfying a given heating requirement. Pond dimensions are determined for house heating, winter crop drying and paper processing in the Richland, Washington area; cost estimates for hypalon-lined ponds of these dimensions are then compared with costs attributed to conventional thermal energy sources used for these purposes. Such comparisons can help guide researchers in determining requirements necessary for the pond to be competitive, e.g. the maximum stabilizing salt content allowable for a competitive pond.     

Determination of the optimal solar investment decision criterion

This paper deals with the validity of the solar investment decision criteria employed in various studies. We begin by examining the life-cycle cost criterion (or positive net present value criterion) commonly used by solar analysts, and subsequently show that, given the theoretical hypotheses of dynamic investment planning and decision making, this criterion is suboptimal for evaluating the economic viability of fuel saver solar systems. The optimal “present cost competitive” criterion is then established and analyzed. The effect of uncertainty is introduced into the analysis by an examination of the payback period criterion. To highlight the differences between these criteria, a comparison of the timing of and net benefits derived from investments in a residential solar space and water heating system made under each criterion is presented.     

Prospects for tapping solar energy on a large scale

As a result of the energy conversion and storage research underway at Oklahoma State University since 1961, several components needed to engineer a continuous-duty energy system operating on replenishable solar energy have been developed to the prototype stage and are being tested. This paper presents and discusses these components and how they fit together in the solar energy systems envisioned for the long-term and immediate future.A simplified economic analysis of solar energy systems is presented, and the calculated generation costs are compared with those of conventional fuel burning systems for different fuel costs, load factors and interest rates. One result of this study is that wind energy systems, costing $125 to $150 per installed kW and pumping power directly into a.c. mains for 20 per cent of the time using the field-modulated generating systems developed at OSU, are competitive with conventional systems costing $250 to $350 per installed kW operating at a load factor of 80 per cent and fuel cost of $0·50 per MBtu. More such comparisons are included in the text of the paper.     

The marginal cost of solar backup

The long-run marginal cost of providing electricity for solar heating and hot water systems is estimated for three utilities and compared with the cost of providing electricity to electric-only systems. All investment, fuel, and operating costs are accounted for. Hot water systems and combined heating and hot water systems are analyzed separately. It is found that the marginal cost for solar backup is no more than the marginal cost of electricity used for purely electric heating and hot water devices and also no more than the incremental cost of normal load growth. For the three utilities studied, there appears to be little basis for rate distinctions between solar devices using electric backup and electric-only heating and hot water devices. “Off-peak storage” heating and hot water devices have a much lower marginal cost than the standard systems; again, there appears to be no basis for distinguishing between solar and electric off-peak devices. Compared with average cost pricing, marginal cost pricing offers benefits to customers using solar and electric heat and hot water, especially if a separate lower rate is adopted for off-peak storage devices; these benefits can amount to several hundred dollars a year. Substantial savings in the use of oil and gas fuels can be achieved if residences using these fuels convert to solar systems, savings not necessarily achievable by a shift, instead, to electric systems.     

Renewable energy in the outback of Australia

Many stations and small communities, particularly Aboriginal Communities, have switched from diesel generators to sensible Remote Area Power Supply (RAPS) systems consisting of wind and/or solar input, battery bank, inverter and generator back-up.The introduction of Synergy Power Corporation's low-wind regime turbines that can hover/reef rather than furl has allowed wind powered RAPS to penetrate markets in the desert communities that were previously considered unsuitable for wind systems. The unique reefing system is described and some interesting case studies given.Solar water pumping and solar powered microwave telecommunications have been common for the past ten years and have proved extremely reliable and have been well accepted.     

Optimal temperature control of solar heating systems

Temperature control systems based on solar and wind energy differ in two important ways from existing fossil fuel systems. One is that solar systems, at least active solar systems, all have some kind of energy storage, the other is that the source of energy in a solar and wind energy system is variable and uncontrollable. Because of these added complications and the high capital investment required for solar and wind energy systems, considerably more sophisticated techniques are required for the design of those systems. In this study, a new technique is applied to the optimal control problem of solar heating systems.     

The benefits of the transition from fossil fuel to solar energy in Libya: A street lighting system case study

The Libyan economy is dominated by the oil and the gas industry which are considered as the primary energy sources for the generating power plants. With the increased energy demands in the near future, Libya will be forced to burn more oil and gas. This, in turn will result in reducing the country revenue, threatening the economy and increasing the CO₂ emission. This triggers the alarm for Libya to an urgent plan to diversify the energy sources through using sustainable energy. The sun showers Libya every day by a huge amount of sunshine, especially during the peaks in the summer days. Recently, the country has been struggling to satisfy its escalating energy demands. The residential and street lighting loads constitute more than 50% of the electricity demands in Libya. Street lighting consumes more than 3.996 TW h, which is around one fifth of the energy demands in Libya. Energy conservation and transition from fossil fuel to renewable energy could have significant profit on the energy sector in Libya. For example, Libya is still relying on the old-fashioned, inefficient and unsustainable street lighting systems. Replacing the old technology lighting systems with up-to-date solar powered lighting system can achieve energy saving and sustainability. In this paper, improving the energy situation in Libya through replacing the high pressure sodium street lighting systems with solar powered LED street lighting systems is investigated. A four km road is chosen as a case study. Four alternatives are analyzed; grid-powered high pressure sodium lamp street lighting system, grid-powered LED lamp street lighting system, stand-alone solar powered LED street lighting system and grid-connected solar powered LED street lighting system. The four options are compared in terms of the capital cost, maintenance cost, total cost, fuel cost and the CO₂ emission. Replacing the high pressure sodium lamp system with LED lamp system saves 75% of energy and reduces the CO₂ emission by 75%. The stand-alone solar powered LED lighting system cuts the CO₂ emission, saves the fuel and is economically feasible. Furthermore, improvement is attained if the solar powered lighting system is connected to the grid where the excess energy is fed to the grid. The two solar powered options are economically feasible and sustainable.     

Performance evaluation of a passive solar building in Western Himalayas

Under the Passive Solar Building Programme, more than 100 buildings have been constructed in the high altitude region of the Indian State of Himachal Pradesh. A policy decision has been taken by the State that all government/semi-government buildings are to be designed and constructed as per passive solar housing technology. The evaluation studies of some of these buildings have been carried out by our group. In the present study, the thermal performance of a passive solar bank building at Shimla, has been evaluated. This solar building incorporates a heat-collecting wall and a roof-top solar air heater with an electric heating backup, sunspaces and double-glazed windows. The monitoring of the building shows that the solar passive features in the building results in comfortable living conditions. The study shows that the high cost central electric/gas/wood-fired heating systems can be replaced by a low cost solar heating system with backup heaters. This will result not only in reducing higher installation costs of these systems but also the annual running and maintenance costs. It is shown that the solar passive features save electricity required for space heating and reduce the heat losses in the building by about 35%. The strategy to be followed for the propagation of passive solar technology on large scale in this Himalayan State or in any other cold hilly region is also presented.     

Optical fibers and solar power generation

A study of the potential use of optical fibers for solar thermal power generation is presented. The main performance characteristics (numerical aperture and attenuation) and typical costs of currently available fibers are discussed. Several approaches to the application of fibers are presented, for centralized (tower, central receiver) and distributed (dish–engine) systems. The overall system design-point efficiency and overall system cost are estimated. A scaling relation between system size and the cost of the fiber component is identified, which severely limits the applicability of fibers to small systems only. The overall system cost for centralized systems is found to be higher than the currently competitive range, even under optimistic assumptions of mass production of major components. A significant reduction in fiber cost is required before the use of fibers for centralized solar power generation can become competitive. In distributed generation using dish/engine systems, however, the use of fibers does achieve competitive performance and costs, comparable to the costs for conventional dish systems.