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Solar photovoltaic systems and trees literature review

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Papers and Articles Related to Solar Panels and Trees[edit]

California’s Solar Shade Control Act; A Review of the Statutes and Relevant Cases 2007 [1]

Abstract: This paper examines Sections 25980–25986 of the California Public Resources Code, known as the Solar Shade Control Act (hereinafter “the Act”), and reviews lawsuits brought under the Act. Through the Act, which was enacted in 1978 and later amended in 2008, the Legislature sought to balance the desired effects of planting trees and shrubs for shade and visual appeal with the desire for increased use of solar energy devices, whose performance can be hindered by shade from nearby vegetation. The Act provides for specific and limited controls of trees and shrubs to protect the use of nearby solar energy systems. However, the extent to which the Act protects solar energy systems from vegetation-created shade is frequently misunderstood, and the subject of many disputes between neighboring property owners. Thus, this paper is intended to provide solar energy users and neighboring tree and shrub owners more information about the content and application of California’s solar laws.

  • California is the leader state promoting solar energy which resulted in adopting laws to protect people's right to access sunlight.
  • This paper examines the laws related to solar access for two reasons. First, the laws are misunderstood by people or solar panel owners. Second, use of solar energy gets more common so most likely more problems and questions will rise in the near future.
  • The act provides specific and limited controls of trees and shrubs to protect the solar energy use nearby.
  • Generally speaking, the Act prohibits a property owner from allowing trees or shrubs to shade an existing solar energy system installed on a neighboring property, provided the shading trees or shrubs were planted after the solar collecting device was installed.
  • The solar collectors that are protected under the act are; Photovoltaics, solar water heating for use in buildings, solar water heating for space heating, solar pool heating.
  • Solar collectors must be set back not less than 5 feet from the property line. And it is height must be not less than 10 feet. If the height is lowered than it must be set back three times as much the height lowered in addition to the 5 feet set back. For instance, if the collector is lowered 2 feet, than the set back distance must be 5 feet + 3x2 = 11 feet.
  • Specifically, Section 25982 of the Act prohibits certain tree owners from planting or allowing a newly planted tree or shrub to cast a shadow over more than ten percent of a solar collector on a neighboring property at any one time during the hours of 10:00 a.m. and 2:00 p.m. However, the Act’s amendment exempts all trees and shrubs planted prior to the time of the installation of a solar collector. In other words, the Act allows trees and shrubs to grow and shade solar panels without penalty as long as they predate the neighboring solar collector.

Hey ,Your Tree is Shading My Solar Panels; California’s Solar Shade Control Act [2]

Abstract: This paper explores laws adopted in the United States at the state level to ensure that a property owner has access to direct sunlight. In particular, it focuses on laws designed to prohibit vegetation on adjacent properties from shading solar energy equipment, such as photovoltaics or solar water heating collectors. The paper compares the laws adopted by states and focuses on California’s Solar Shade Control Act as a model for other states. It provides a detailed analysis of the provisions of the Act and a review of cases brought under it.

  • The laws can be grouped under four categories.

1)_ Prohibition of Covenants, conditions and restrictions. 2)_ Solar Easement 3)_ Local Zoning Authority to Adopt Solar Access Regulations 4)_ Solar Shading

  • Section 25983 provides that ‘‘the person who maintains or permits the tree or shrub to be maintained’’ can be liable if they violate the Act.
  • Prior to its amendment in 2008, violators of the Act could be criminally prosecuted and convicted of maintaining a public nuisance for allowing their trees to shade neighboring solar collectors.
  • After the Act’s amendment, violators are no longer considered criminal.
  • Section 25984(a) states that the Act does not apply to trees or shrubs planted prior to the installation of a solar collector. Therefore, trees or shrubs planted before a solar collector is installed and later grow to cast a shadow over more than 10% of the solar collector are completely exempt from the Act.
  • The Act both explicitly and implicitly exempts certain property owners and certain trees and shrubs from the Act. Indeed, the solar collector owner’s right to sunlight is not absolute.
  • Section 25984(b) of the Act specifically exempts all trees planted, grown, or harvested on timberland or on land devoted to the production of commercial agricultural crops.
  • if a tree planted prior to the installation of the solar collector dies, or is removed for the protection of public health, safety, or the environment, and is subsequently replaced, the replacement tree is exempt from the Act, even if it shades the solar collector in a way that would otherwise violate the Act.
  • Section 25984(d) exempts from the provisions of the Act any ‘‘tree or shrub that is subject to a city or country ordinance
  • Section 25985(a) of the Act allows any city or unincorporated areas of a county to adopt an ordinance exempting itself from the Act.18 This exemption applies only to trees planted and maintained by the municipality itself, and not to trees owned by private citizens.
  • Important key questions for the Solar Collector Owner:

1)_ Was the tree or shrub in question planted after the solar collector’s installation? 2)_ Was the solar collector installed pursuant to Section 25981(d)’s setback requirements? 3)_ Does the solar collector meet the statutory definition of a ‘‘solar collector’’ provided in Section 25981? 4)_ Does the neighboring tree or shrub shade more than 10% of the solar collector between 10:00 AM and 2:00 PM local standard time?

  • Important key questions for the Tree-Shrub owner:

1)_ Does the tree or shrub shade more than 10% of the solar collector between 10:00 AM and 2:00 PM local standard time? 2)_ Was the tree or shrub in question planted after the solar collector was installed? 3)_ Did the solar collector owner, or their agent, provide written notice requesting compliance with the requirements of Section 25982?

  • Tree or Shrub owner may not be violating the act if he/she can answer the questions:

1)_ Was the solar collector designed and intended to offset more than the building’s electricity demand? 2)_ Is the tree or shrub in question owned by a municipality that has passed an ordinance exempting itself from the Act? 3)_ Is the tree or shrub subject to a city or county ordinance? 4)_ Is the tree or shrub in question growing on land designated as timberland or agricultural land? 5)_ Are the trees or shrubs in question part of a passive cooling and heating strategy in which net energy savings from the passive solar system are demonstrably greater than those of the shaded solar collector?


Trees Block Solar Panels, and a Feud Ends in Court [3]

Abstract: Trees — redwoods, live oaks or blossoming fruit trees — are usually considered sturdy citizens of the sun-swept peninsula south of San Francisco, not criminal elements. But under a 1978 state law protecting homeowners’ investment in rooftop solar panels, trees that impede solar panels’ access to the sun can be deemed a nuisance and their owners fined up to $1,000 a day. The Solar Shade Act was a curiosity until late last year, when a dispute over the eight redwoods(a k a Tree No. 1, Tree No. 2, Tree No. 3, etc.) ended up in Santa Clara County criminal court.

The Solar Shade Control Act— From Trees Versus Solar to Trees and Solar? [4]

Abstract: Can bad cases ever make good law? Maybe in the case of homeowners Richard Treanor and Carolynn Bissett who were criminally prosecuted under the Solar Shade Control Act3 (“SSCA”) because their pre-existing trees cast shadows over their neighbor’s solar panels. Until the recent enactment of an amendment to the SSCA, property owners could face criminal prosecution if their trees grew to shade a neighbor’s solar panels, with no consideration given to whether the trees were planted before the panels were installed.

State of Solar Rights Across the United States [5]

Abstract: Solar energy is cheap, abundant, and readily available. Solar energy could help the United States to decrease (and, potentially, eliminate) its dependency on oil imports. However, the rate of solar technology adoption has been slow, to say the least. This paper is an attempt to summarize different ways in which state and local governments, courts, and private citizens address challenges arising from solar power adoption.

Legal Aspects of Solar Energy: Statutory Approaches for Access to Sunlight [6]

Part of the Introduction: A solar energy collector without sunlight is useless; solar energy users require unobstructed access to sunlight. Therefore, it is imperative for the solar energy user to secure the legal right to unobstructed sunlight necessary for his solar-powered system.

Solar Rights [7]

Abstract: The rights to access and to harness the rays of the sun - solar rights - are extremely valuable. These rights can determine whether and how an individual can take advantage of the sun’s light, warmth, or energy, and they can have significant economic consequences. Accordingly, for at least two thousand years, people have attempted to assign solar rights in a fair and efficient manner. In the United States, attempts to assign solar rights have fallen short. A quarter century ago, numerous American legal scholars debated this deficiency. They agreed that this country lacked a coherent legal framework for the treatment of solar rights, especially given the emergence of solar collector technology that could transform solar energy into thermal, chemical, or electrical energy. These scholars proposed several legal regimes that they believed would clarify solar rights and facilitate increased solar collector use. Very little has changed since this debate about solar rights began. Although some jurisdictions have experimented with scholars’ suggestions, reforms have not been comprehensive, and solar rights are guaranteed in very few places. At least in part because of the muddled legal regime, and despite numerous technological advances that have reduced the cost of solar collectors, only one percent of our nation’s energy currently comes from the sun. In this context, this Article aims to reinvigorate and refocus the scholarly debate about solar rights. The Article first explains why solar rights are valuable to both individuals and to the country as a whole. It then analyzes three methods by which solar rights can be allocated: express agreements between property owners, governmental permit systems or zoning ordinances, and court assignments that result from litigation. Although this Article analyzes the concerns of both solar rights seekers and possible burdened parties with respect to current law; it does not fully address the possible solution to the problem of solar rights. Instead, this Article sets the stage for a second piece, 'Modern Lights,' simultaneously being published in the University of Colorado Law Review.

Shadows on the Cathedral: Solar Access Laws in a Different Light [8]

Abstract: Unprecedented growth in rooftop solar energy development is drawing increased attention to the issue of solar access. To operate effectively, solar panels require un-shaded access to the sun’s rays during peak sunlight hours. Some landowners are reluctant to invest in rooftop solar panels because they fear that a neighbor will erect a structure or grow a tree on nearby property that shades their panels. Existing statutory approaches to protecting solar access for such landowners vary widely across jurisdictions, and some approaches ignore the airspace rights of neighbors. Which rule regime for solar access protection best promotes the efficient allocation of scarce airspace, within the constraints of existing law? This Article applies Calabresi and Melamed’s “Cathedral” framework of property rules and liability rules to compare and analyze existing solar access laws and to evaluate a model solar access statute recently drafted under funding from the US Department of Energy. Surprisingly, the Article concludes that a statute implementing the Cathedral model’s seldom-used “Rule Four” is best suited for addressing solar access conflicts.

The House of the Rising Sun: Homeowners' Associations, Restrictive Covenants, Solar Panels, and the Contract Clause [9]

Abstract: Private land-use controls in the form of restrictive covenants promulgated by homeowners' associations prevent the effective use and expansion of alternative energy by prohibiting or restricting the use of solar energy devices based on concerns of uniformity and aesthetics. The problem of homeowners' associations discriminating against solar energy has received less attention than the problem actually merits. The best possibility for invalidating these covenants and moving renewable energy forward is legislative action. Although some states have taken action on this issue, state statutes have significant and serious deficiencies. Effective state statutes require both more breadth and more specificity. State statutes that invalidate restrictive covenants discriminating against solar energy implicate, but do not violate, the U.S. Constitution's Contract Clause. These statutes remain within the legitimate exercise of state police power.

Solar Siting Ordinances [10]

Abstract: This Essential Info Packet provides an extensive collection of sample ordinances on solar access, solar siting, and solar energy systems large and small, along with background articles and examples of how communities are adding solar provisions to their comprehensive plans.

Solar Access Ordinances [11]

Abstract: This Essential Info Packet provides an extensive collection of sample ordinances on solar access, solar siting, and solar energy systems large and small, along with background articles and examples of how communities are adding solar provisions to their comprehensive plans.

Zoning Changes for Distributed Wind and Solar Energy Production in Blacksburg [12]

Part of the Introduction: The goal of this report is to evaluate what specific changes could be made to the Blacksburg zoning ordinance to support distributed wind and solar energy production. Zoning is a powerful tool that local governments use to control the built environment and implement the comprehensive plan. Zoning ordinances regulate the permitted uses of land, lot sizes, density, building heights, parking, and many other requirements. By removing existing impediments in the zoning code that prevents citizens from implementing small-scale wind and solar, a town can significantly reduce its greenhouse gas emissions.

Solar Energy Articles and Reports [13]

Solar in the Comprehensive Plan [14]

Siting and Solar Access [15]

Abstract: This fact sheet outlines the relationship between site layout, solar access and energy smart house design. It also provides a guide to selecting a lot with good solar access and includes tips on siting a home on a block and internal planning for maximum energy efficiency.

California's Solar Access Laws [16]

Abstract: California has several laws designed to encourage solar access and prevent restrictions on solar energy systems. These laws address municipal restrictions, residential landscaping, and homeowner association restrictions.

Self-shading losses of fixed free-standing PV arrays [17]

Abstract: The energy yield of a photovoltaic (PV) system with fixed free-standing PV arrays is affected also by the self-shading effects. The rows of PV modules in arrays may partially shade the PV modules in the rows behind. In this paper the effects of the row distance on the PV system’s energy yield are evaluated. The estimation of the self-shading losses by the irradiation losses simply overestimates the losses; therefore we developed a simulation model to simulate the real energy loss due to shading of the preceding row in a PV system. The model demonstrates that the self-shading energy losses are at commonly used distances between rows from 20 to 40% lower than the irradiation losses at the modules’ bottom considering the shading conditions. The self-shading energy loss is studied in the case of Ljubljana, Slovenia which may refer to the whole Central Europe. To estimate the self-shading losses a technologyand with parameter modifications also location-independent empirical equation based on module-tocell width ratio was derived and validated.

Solar access of residential rooftops in four California cities [18]

Abstract: Shadows cast by trees and buildings can limit the solar access of rooftop solar-energy systems, including photovoltaic panels and thermal collectors. This study characterizes residential rooftop shading in Sacramento, San Jose, Los Angeles and San Diego, CA. Our analysis can be used to better estimate power production and/or thermal collection by rooftop solar-energy equipment. It can also be considered when designing programs to plant shade trees.

Constructal design of solar energy-based systems for buildings [19]

Abstract: One of the major issues confronting users of solar energy-based systems is the relatively low efficiency of these systems when compared with fossil fuel-based systems. In this paper we take a fresh look at the generation of architecture of these systems based on the constructal theory. Three different systems are investigated: a shading system to control the incoming of solar radiation during the summer and the winter, a bundle of pipes to warm a room, and a distillation system integrated in a roof. The constructal principle invoked in this paper shows that geometrical form of systems can be deduced from a single principle and provides designers with tools for their conceptual design.

A Comprehensive review of solar access law in the united states [20]

Part of the Executive Summary: Solar energy systems require direct access to sunlight to operate efficiently. The installation of a solar energy system on a new or existing building requires exterior modifications that are subject to building codes and private regulation. This report reviews the ability of existing law and regulation to protect solar access and recommends specific measures to improve solar access.

City of Shakopee 2030 Comprehensive Plan; Solar Access Protection [21]

Part of the Paper: Trees, shrubs, turf and other ground covers are among the best exterior solar and wind control devices. During summer months vegetation controls reflection/absorption of heat radiation, provides shade for walls and ground surfaces, and creates insulating dead air spaces. Plants can insulate buildings from intense heat and protect cooling equipment from the effects premature wear that can be the result of rapid exterior temperature changes. Plants serve double duty by absorbing day heat and then releasing it slowly at night, thereby cooling daytime temperatures and warming and moderating evening temperatures. Overstore deciduous trees can provide cooling effects during warm months while allowing maximum solar penetration during cooler seasons.

Don't Take My Sunshine Away: Right-to-Light and Solar Energy in the Twenty-First Century [22]

Part of the Introduction: This note will recount the history of property owners' right-to-light, analyze current solar energy statutes, examine right-to-light case law in the United States and study the effects that easements and the Fifth Amendment's "takings clause" and police power have on solar energy use.

Protecting Solar Access [23]



Lit Review on Trees, Their Shading Factor and Urban Tree Planting[edit]

Calculation procedure of the shading factor under complex boundary conditions [24]

Abstract: The objective of this study is the development of a calculation procedure of the shading factor under complex boundary conditions. The algorithms have been implemented in a software tool written in MATLAB language. It can provide for the value of the shading factor on a generically oriented and tilted surface. After setting the site and the time for the simulation, generic-shaped windows can be modeled. The external environment, which can be imported from DXF files, can include a horizon profile, generic-shaped obstructions and vegetation. The calculation can be performed for every sky condition: clear, average or generic. In addition, the simulation can be run to obtain instantaneous, daily average or monthly average shading factor values.

Effect of tree shades in urban planning in hot-arid climatic regions. [25]

Abstract: The present study is carried out for dry hot climate places, where excessive solar heating is felt throughout the year. The effect of tree shadowing buildings is found to reduce heating loads; hence trees have a beneficial effect in energy economics. The emerging economic value of tree shadows in hot climate cities grants the development of an appropriate simulation numerical method to establish relative advantages on energy savings related to dwelling envelopes. The results demonstrate that large trees can provide up to 70% shade during spring and autumn, thus saving a very large amount of energy along the whole year. Hence, economic value of larger trees is greater than that of younger species.

The effect of urban leaf area on summertime urban surface kinetic temperatures: A Terre Haute case study [26]

Abstract: The urban heat island effect (UHIE) has been documented in many temperate region cities. One cause of the UHIE is the eplacement of green spaces with impervious materials as urbanization commences and the city builds up and fills in. During the summer, elevated urban temperatures result in increased electricity usage, higher pollution levels, and greater resident discomfort. Through evapotranspiration and the interception of solar radiation, increasing urban tree canopy cover can help mitigate the UHIE. While this is universally accepted, the exact statistical relationship between urban leaf area (as measured by leaf area index, LAI) and urban temperatures has not been extensively studied. In a case study conducted in urban/suburban Terre Haute, Indiana, USA, simple linear regression was employed to quantify the relationship between in situ ceptometer LAI measurements and surface kinetic temperatures (SKTs) measured using thermal atellite imagery acquired at 1100 local time. For the 143 sample sites located in the study area, LAI accounted for 62% of the variation in surface temperature. For every unit increase in LAI, surface temperature decreased by 1.2 1C.

Effects of individual trees on the solar radiation climate of small buildings [27]

Abstract: Under clear skies, a mid-sized sugar maple tree (Acer saccharum Marsh.) reduced irradiance in its shade on a south-facing wall by about 80% when in leaf, and by nearly 40% when leafless. Reductions by a similar-sized London plane (Platanus acerifolia W.) were generally slightly smaller. The percentage reductions varied with the fraction (DR) of diffuse radiation, and could be approximated by regressions with DR' as the independent variable.

Energy savings from tree shade [28]

Abstract: Trees cast shade on homes and buildings, lowering the inside temperatures and thus reducing demand for power to cool these buildings during hot times of the year. Drawing from a large sample of residences in Auburn, Alabama, we develop a statistical model that produces specific estimates of the electricity savings generated by shade-producing trees in a suburban environment. This empirical model links residential energy consumption during peak summer (winter) months to average energy consumption during nonsummer/ non-winter months, behaviors of the occupants, and the extent, density, and timing of shade cast on the structures. Our estimates reveal that tree shade enerally is associated with reduced (increased) electricity consumption in the summertime (wintertime). In summertime, energy savings are maximized by having dense shade. In wintertime, energy consumption increases as shade percentage in the morning, when outdoor temperatures are at their lowest, increases.

The Effect of Gainesville's Urban Trees on Energy Use of Residential Buildings [29]

Part of the Paper: A city's trees reduce its energy use year round. In warm months trees shade buildings and provide evaporative ooling, and in cold months they block icy winter winds. Trees near a building tend to reduce air conditioning use in that building in the summer months. The same trees can either increase or decrease energy use in a building during the winter months depending where the trees are in relation to the building. Knowing the size of a given building and the sizes and positions of the trees near it will enable us to place an economic value on the trees based on how much they reduce or increase energy use in the building.

The value of shade: Estimating the effect of urban trees on summertime electricity use [30]

Abstract: We estimated the effect of shade trees on the summertime electricity use of 460 single-family homes in Sacramento, California. Results show that trees on the west and south sides of a house reduce summertime electricity use, whereas trees on the north side of a house increase summertime electricity use. The current level of tree cover on the west and south sides of houses in our sample reduced summertime electricity use by 185 kWh (5.2%), whereas north-side trees increased electricity use by 55 kWh (1.5%). Results also show that a London plane tree, planted on the west side of a house, can reduce carbon emissions from summertime electricity use by an average of 31% over 100 years.

Peak power and cooling energy savings of high-albedo roofs [31]

Abstract: In the summers of 1991 and 1992, we monitored peak power and cooling energy savings from high-albedo coatings at one house and two school bungalows in Sacramento, California. We collected data on air-conditioning electricity use, indoor and outdoor temperatures and humidities, roof and ceiling surface temperatures, inside and outside wall temperatures, insolation, and wind speed and direction. Applying a high-albedo coating to one house resulted in seasonal savings of 2.2 kWh/d (80% of base case use), and peak demand reductions of 0.6 kW. In the school bungalows, cooling energy was reduced 3.1 kWh/d (35% of base case use), and peak demand by 0.6 kW. The buildings were modeled with the DOE-2.1E program. The simulation results underestimate the cooling energy savings and peak power reductions by as much as twofold.

Shade trees reduce building energy use and CO2 emissions from power plants [32]

Abstract: Urban shade trees offer significant benefits in reducing building air-conditioning demand and improving urban air quality by reducing smog. The savings associated with these benefits vary by climate region and can be up to $200 per tree. The cost of planting trees and maintaining them can vary from $10 to $500 per tree. Tree-planting programs can be designed to have lower costs so that they offer potential savings to communities that plant trees. Our calculations suggest that urban trees play a major role in sequestering CO2 and thereby delay global warming. We estimate that a tree planted in Los Angeles avoids the combustion of 18 kg of carbon annually, even though it sequesters only 4.5–11 kg (as it would if growing in a forest). In this sense, one shade tree in Los Angeles is equivalent to three to five forest trees. In a recent analysis for Baton Rouge, Sacramento, and Salt Lake City, we estimated that planting an average of four shade trees per house (each with a top view cross section of 50 m2) would lead to an annual reduction in carbon emissions from power plants of 16,000, 41,000, and 9000 t, respectively (the per-tree reduction in carbon emissions is about 10–11 kg per year). These reductions only account for the direct reduction in the net cooling- and heating-energy use of buildings. Once the impact of the community cooling is included, these savings are increased by at least 25%.

Building cluster and shading in urban canyon for hot dry climate Part 1: Air and surface temperature measurements [33]

Abstract: Under low latitude conditions, minimization of solar radiation within the urban environment may often be a desirable criterion in urban design. The dominance of the direct component of the global solar irradiance under clear high sun conditions requires that the street solar access must be small. It is well known that the size and proportion of open spaces has a great influence on the urban microclimate.

Effect of adjacent shading on the thermal performance of residential buildings in a subtropical region [34]

Abstract: There are various architectural features of a residential building that can influence its indoor climate and electricity consumption, such as thermal insulation, window size, glazing material, albedo of building façade and orientation. In addition to these architectural features, shading effects (either by external objects or by the building itself) can also affect the thermal performance of a building. External shading effects are mainly caused by nearby trees or buildings, while shading effect imposed by the building itself usually depends on the layout design of the building, i.e. building shape and layout arrangement of the flats on each floor. Some flats in a building may receive a shading effect from adjacent flats located in the same building block. When architects or building designers conduct the layout design of a building, a number of factors such as building regulations, site limitations, scenic view, noise control, natural ventilation and daylight utilization will be considered. The thermal performance of a building is one of the major issues that should be taken into account. The objective of this study is to assess the thermal performance of residential buildings under the effect of adjacent shading in subtropical Hong Kong. A literature survey was carried out to identify typical layout designs of residential buildings from the past two decades. Building energy simulations were conducted for residential building blocks with different layout designs. It is found that adjacent shading effect has a substantial impact on the thermal performance of residential buildings. The findings are reported in this paper.

Impact of shading air-cooled condensers on the efficiency of air-conditioning systems [35]

Abstract: Shading is a technique used to reduce the cooling demand in buildings and save energy. This paper investigates the possibility of reducing the electrical demand and saving energy by shading the condensers of air-conditioning (A/C) equipment. A limiting analysis compares the performance of several A/C systems with ideal shade to those with ideal solar heat gain. The comparison is based on a theoretical model and data from equipment catalogs. The results show that the theoretical increase in the coefficient of performance (COP) due to shading is within 2.5%. Furthermore, this small improvement in ideal efficiency decreases at higher ambient temperatures, when enhancements to efficiency are more needed. A sensitivity analysis shows that the small COP enhancement is not significantly affected by assumed variables. The actual efficiency improvement due to shading is not expected to exceed 1%, and the daily energy savings will be lower. The findings indicate that condenser shading alone, without evapo-transpiration, is not an effective measure to improve efficiency or save energy.

[http://www.arct.cam.ac.uk/PLEA/ConferenceResources/PLEA2004/Proceedings/p0606final.pdf The thermal effects of city greens on surroundings under the tropical climate [36]]

Abstract: In Singapore, rapid population influx has led to demands for converting natural areas to pubic housing. The heat island in Singapore city has been documented. However, less attention has been placed on the cooling effect of city’s green areas. To address this issue, temperature and humidity measurements were made in two big city green areas. One is the city’s natural reserve - Bukit Batok Nature Park (36 ha) and the other is a neighbourhood park - Clementi Woods (12 ha). The measurements were conducted at both vegetated areas and their surroundings. The results indicated the cooling effects of city greens are remarkable not only on vegetated areas but surrounding built environments. To further explore the role of the green area on moderating the microclimate, two simulation programmes, TAS and Envi-met, were employed respectively for the two parks. The aims are to explore the patterns of energy consumptions of a typical commercial building near to Bukit Batok Nature Park and different thermal conditions with and without Clementi Woods.

Performance evaluation of green roof and shading for thermal protection of buildings [37]

Abstract: The present paper describes a mathematical model for evaluating cooling potential of green roof and solar thermal shading in buildings. A control volume approach based on finite difference methods is used to analyze the components of green roof, viz. green canopy, soil and support layer. Further, these individual decoupled models are integrated using Newton’s iterative algorithm until the convergence for continuity of interface state variables is achieved. The green roof model is incorporated in the building simulation code using fast Fourier transform (FFT) techniques in Matlab. The model is validated against the experimental data from a similar green roof-top garden in Yamuna Nagar (India), and is then used to predict variations in canopy air temperature, entering heat flux through roof and indoor air temperature. The model is found to be very accurate in predicting green canopy-air temperature and indoor-air temperature variations (error range 73.3%, 76.1%, respectively). These results are further used to study thermal performance of green roof combined with solar shading. Cooling potential of green roof is found adequate (3.02kWh per day for LAI of 4.5) to maintain an average room air temperature of 25.7 1C. The present model can be easily coupled to different greenhouse and building simulation codes.

An experimental investigation of the effect of shading with plants for solar control of buildings [38]\

Abstract: An experimental investigation was carried out to analyze the effect of using trees for solar control of buildings by shading. Several physical parameters were measured in two areas, on the same facade, of a building at the Agricultural University of Athens; high trees shaded one area, while the other was clear from any shadow. Comparisons were made for a hot summer period between the physical parameters measured in the shaded and the unshaded areas regarding the air and wall surface temperature, the heat exchanges between the wall surface and the surrounding environment, the wind speed and the humidity of the air. The results showed that plants constitute an excellent passive system for solar control of buildings offering significant advantages over conventional artificial sunscreens.

Tree structure influences on rooftop-received solar radiation [39]

Abstract: The influence of trees on the solar radiation intercepted by buildings is an important aspect in understanding the complex inter-relations between urban form and environmental conditions. In this paper we describe the application of laser remote sensing technologies to examine the structural properties of the urban surface and present methods to quantify the diurnal and seasonal impact of trees on solar radiation in these areas. LiDAR (light detection and ranging) data provides the three dimensional information required to populate geographic information system-based radiation models, which are produced at hourly intervals for the summer and winter solstice and equinox in a midlatitude North American city. Structural information for buildings and trees are extracted for individual lots and related to direct and diffuse radiation for urban residential dwellings. Results indicate that trees on average reduce 38% of the total solar radiation received by residential building rooftops. Additionally, strong correlations were found between measures of tree structure (average height, tree height variability, and normalized tree volume) and intercepted direct radiation in the summer, while the relationships with diffuse radiation were consistent throughout the year. Finally, an examination of the hourly relation between tree structural attributes and rooftop radiation estimates demonstrates substantial variation not apparent in the assessment of daily averages. Discussion of this research explains the application of LiDAR data to automate urban vegetation analysis and to inform planners of the cumulative impacts of trees on energy management initiatives in cities.

Energy saving by proper tree plantation [40]

Abstract: A model is presented to predict the e}ect of trees as passive cooling options on buildings[ A computer program is written to calculate hourly cooling load requirements by the numerical solution of the energy balance equation for the building[ This simulation is validated by comparison with _eld data taken from an actual house in Shiraz\ Iran[ A guideline is presented for optimum tree plantation concerning energy saving[ Results indicate that for the house under study "of popular size in Shiraz# cooling loads may be reduced by 10-40% by appropriate tree plantation.

Simulation of Tree Shade Impacts on Residential Energy Use for Space Conditioning In Sacramento [41]

Abstract: Tree shade reduces summer air conditioning demand and increases winter heating load by intercepting solar energy that would otherwise heat the shaded structure. We evaluate the magnitude of these effects here for 254 residential properties participating in a utility sponsored tree planting program in Sacramento, California. Tree and building characteristics and typical weather data are used to model hourly shading and energy used for space conditioning for each building for a period of one year. There were an average of 3.1 program trees per property which reduced annual and peak (8 h average from 1 to 9 p.m. Pacific Daylight Time) cooling energy use 153 kWh (7.1%) and 0.08 kW (2.3 %) per tree, respectively. Annual heating load increased 0.85 GJ (0.80 MBtu, 1.9%) per tree. Changes in cooling load were smaller, but percentage changes larger, for newer buildings. Averaged over all homes, annual cooling savings of $15.25 per tree were reduced by a heating penalty of $5.25 per tree, for net savings of $10.00 per tree from shade. We estimate an annual cooling penalty of $2.80 per tree and heating savings of $6.80 per tree from reduced wind speed, for a net savings of $4.00 per tree, and total annual savings of $14.00 per tree ($43.00 per property). Results are found to be consistent with previous simulations and the limited measurements available.

Improved estimates of tree-shade effects on residential energy use [42]

Abstract: Tree-shade alters building cooling and heating loads by reducing incident solar radiation. Estimates of the magnitude of this efffect, and how it is influenced by urban forest structure (e.g. tree size and location), are difficult due to the complexity inherent in tree-sun-building interactions. The objective of this paper is to present a simplified method for making these estimates appropriate for neighborhood and larger scales. The method uses tabulated energy use changes for a range of tree types (e.g. size, shape) and locations around buildings (lookup tables), combined with frequency of occurrance of trees at those locations. The results are average change in energy use for each tree type that are not explicitly dependent on tree location. The method was tested by comparison to detailed simulations of 178 residences and their associated trees in Sacramento, California. Energy use changes calculated using lookup tables matched those from detailed simulations within ± 10%. The method lends itself to practical evaluation of these shading effects at neighborhood or larger scales, which is important for regional assessments of tree effects on energy use, and for development of tree selection and siting recommendations for proposed conserving planting programs.

Tree structure influences on rooftop-received solar radiation [43]

Abstract: The influence of trees on the solar radiation intercepted by buildings is an important aspect in understanding the complex inter-relations between urban form and environmental conditions. In this paper we describe the application of laser remote sensing technologies to examine the structural properties of the urban surface and present methods to quantify the diurnal and seasonal impact of trees on solar radiation in these areas. LiDAR (light detection and ranging) data provides the three dimensional information required to populate geographic information system-based radiation models, which are produced at hourly intervals for the summer and winter solstice and equinox in a midlatitude North American city. Structural information for buildings and trees are extracted for individual lots and related to direct and diffuse radiation for urban residential dwellings. Results indicate that trees on average reduce 38% of the total solar radiation received by residential building rooftops. Additionally, strong correlations were found between measures of tree structure (average height, tree height variability, and normalized tree volume) and intercepted direct radiation in the summer, while the relationships with diffuse radiation were consistent throughout the year. Finally, an examination of the hourly relation between tree structural attributes and rooftop radiation estimates demonstrates substantial variation not apparent in the assessment of daily averages. Discussion of this research explains the application of LiDAR data to automate urban vegetation analysis and to inform planners of the cumulative impacts of trees on energy management initiatives in cities.

Effect of crown shape and tree distribution on the spatial distribution of shade [44]

Abstract: A method for calculating the light extinction probability caused by a forest canopy is presented. With the calculation procedure, it is possible to examine the effect of crown shape, stand density and spatial distribution of trees on the spatial distribution of light extinction probability or on the total shaded area caused by the canopy. At low sun elevations, the momentary projection area of a single crown is greater the more vertically extended the crown is, if the crown volume is held constant. When a longer time period is concerned, the area where the average extinction probability exceeds some arbitrary value is greatest for umbrella-like, horizontally extended crowns. The same is true for a single tree and for a forest stand. When the stand density is low or the tree crown is narrow, the spatial distribution of trees has only a small effect on the amount of shaping; the total amount of shading in random distribution is almost the same as in systematic distribution. In a stand where the total horizontal projection area of crown cones is high, the spatial distribution of trees should be systematic for effective light interception.

[http://www.firelandsec.com/documents/tree_growth_study.pdf Tree Growth Study [45]

Solar Panels, Solar Siting[edit]

The strategic siting and the roofing area requirements of building integrated photovoltaic solar energy generators in urban areas in Brazil [46]

Abstract: Building-integrated photovoltaic (BIPV) generators are typically small and distributed solar power plants that occupy virtually no space because they are part of the building envelope, and they generate power at point of use. A more widespread use of grid-connected photovoltaics (PV) is hindered by a number of reasons which include the declining, but still high costs of the photogenerated kilowatt hour, and the lack of knowledge about the benefits of distributed generation with PV in the urban environment. When strategically sited, PV generators integrated to building fac¸ades and rooftops in urban areas at limited penetration levels can benefit local feeders with these distributed ‘‘negative loads’’. A number of studies have been published, with learning curves demonstrating the cost-reduction potential of large-scale PV production, and in some markets the cost of PV electricity is approaching residential tariffs, the so-called grid parity. Due to the intermittent nature of the solar radiation resource, PVis considered non-despatchable power, but under some conditions, in sunny urban areas with electricity load curves dominated by airconditioning loads, there is a high correlation between PV generation and feeder loads. In these situations, a considerable fraction of a given PV generator can be considered despatchable power. In this work we assess the potential of building-integrated, grid-connected PV generation in the state capital Floriano´polis, in South Brazil. The deployment of six different commercially available PV technologies is compared with total roof area availability, solar generation profiles, and local feeder load curves for a selected number of urban areas in the city. Our results demonstrate the advantages of strategically siting PV generators in the urban environment.

Siting of Active Solar Collectors and Photovoltaic Modules [47]

Abstract: To install a solar energy system properly, it is important to understand the siting and tilt requirements for solar collectors. This is true for all types of solar collectors, whether they are flat plate collectors for heating water, or photovoltaic modules for generating electricity. The flat plate collectors or photovoltaic modules must be oriented and tilted to obtain maximum solar radiation and to avoid unwanted shading. Evaluating these factors at the outset is essential to determine if your proposed site is suitable for collecting solar energy and to ensure that your system operates efficiently.

Guide to Installing a Solar Electric System [48]

Abstract: This guide is designed to provide Seattle City Light customers with information on grid-connected solar electric systems. It provides background on solar electric systems, the components required, and outlines the steps to take if you want to install and interconnect a system to the utility grid.

City of Santa Barbara, SOLAR ACCESS HEIGHT LIMITATIONS [49]

Part of the Paper: Use the following steps to determine whether your structure complies with the Solar Access Ordinance (SBMC Chapter 28.11). This ordinance only applies in residential zones. The purpose of the Solar Access Ordinance is to ensure that your building does not cast a significant shadow on your neighbor's building. This is determined by projecting a shadow that your building would cast on December 21, the day when the sun is lowest in the sky, and your building casts its longest shadow.

Most Updated List of Trees in Midwest, USA[edit]

No: Class Species Age Height (Feet) Growth
1 Conifer Evergreen Abies Balsamea (Linnaeus) Miller 150 60 Fast
2 Conifer Evergreen Picea Glauce (Moench) Voss 200 or more 70 N/A

Relevant Books[edit]

  • Trees of Michigan [50]
  • Forest Trees of Illinois [51]
  • Native Trees of the Midwest [52]

Relevant Web Pages[edit]

Urban Forest Ecosystem Institute (UFEI)

Heliodon Model

Heliodon™ version 2.7-02, Heliodon Software

References[edit]

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  2. Scott Anders, Taylor Day, and Carolyn Adi Kuduk, Hey ,Your Tree is Shading My Solar Panels; California’s Solar Shade Control Act.
  3. Felicity Barringer, Trees Block Solar Panels, and a Feud Ends in Court, New York Times, April, 2008.
  4. Serena Patitucci Torvik, The Solar Shade Control Act— From Trees Versus Solar to Trees and Solar?, Miller & Starr Real Estate Newsalert, vol.19, no.3, January 2009.
  5. Novikov, Igor V., State of Solar Rights Across the United States, July 20, 2009
  6. John William Gergacz, Legal Aspects of Solar Energy: Statutory Approaches for Access to Sunlight, 10 B.C. Envtl. Aff. L. Rev. 1, 1982.
  7. Bronin, Sara C., Solar Rights, (September 26, 2009). Boston University Law Review, Vol. 89, p. 1217, 2009.
  8. Rule, Troy A., Shadows on the Cathedral: Solar Access Laws in a Different Light (December 1, 2009). University of Missouri School of Law Legal Studies Research Paper No. 2009-24; University of Illinois Law Review, Vol. 2010, p. 851
  9. K. CAFFREY,The House of the Rising Sun: Homeowners' Associations, Restrictive Covenants, Solar Panels, and the Contract Clause, Natural resources journal [0028-0739], 2010 vol:50 pg:721.
  10. Solar Siting Ordinances PAS Essential Info Packets; Planning and Zoning for Solar Energy (PAS EIP-30)
  11. Solar Access Ordinances PAS Essential Info Packets; Planning and Zoning for Solar Energy (PAS EIP-30)
  12. Lauryn Douglas, Jenny Hazlett, Jenna Klym, Michael Shroyer, Jennifer Thangavelu, UAP 5174, Fall 2009.
  13. Solar Energy Articles and Reports, PAS Essential Info Packets; Planning and Zoning for Solar Energy (PAS EIP-30)
  14. Solar in the Comprehensive Plan, PAS Essential Info Packets; Planning and Zoning for Solar Energy (PAS EIP-30)
  15. Sustainable Energy Info Fact Sheet; online at http://www.sustainability.vic.gov.au/resources/documents/Siting_and_solar_access.pdf
  16. Kurt Newick & Andy Black, California's Solar Access Laws, 2005.
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  19. Miguel A. F., 2008. Constructal design of solar energy-based systems for buildings. Energy and Buildings 40: 1020–1030.
  20. Colleen McCann Kettles, A Comprehensive review of solar access law in the united states, Florida Solar Energy Research and Education, October, 2008.
  21. City of Shakopee 2030 Comprehensive Plan Solar Access Protection, online at: http://www.ci.shakopee.mn.us/pages/2030CompPlan/12%20Solar%20Access.pdf
  22. Tawny L. Alvarez,Don't Take My Sunshine Away: Right-to-Light and Solar Energy in the Twenty-First Century, article 3, vol. 28, issue 3, Spring, 2008.
  23. Troy A. Rule, Protecting Solar Access University of Missouri, Solar America Cities - Third Annual Meeting, April 15, 2010.
  24. Cascone, Y. Corrado, V., Serra, V., Calculation procedure of the shading factor under complex boundary conditions.' Solar Energy 85: 2524–2539, 2011,
  25. Gómez-Munoz, V.M., Porta-Gándara, M.A., Fernández, J.L., Effect of tree shades in urban planning in hot-arid climatic regions. Landscape and Urban Planning 94: 149–157, 2010.
  26. Hardin, P. J., Jensen, R. R., The effect of urban leaf area on summertime urban surface kinetic temperatures: A Terre Haute case study. Urban Forestry & Urban Greening 6: 63–72, 2007
  27. Heisler G.M., Effects of Individual Trees on the solar radiation climate of small buildings. Urban ecology, 9: 337-359, 1986
  28. Pandit, R., Laband, D. N., Energy savings from tree shade. Ecological Economics 69: 1324–1329, 2010
  29. Escobedo, F., Seitz, J. A., Zipperer, W., The Effect of Gainesville's Urban Trees on Energy Use of Residential Buildings. University of Florida, IFAS extension, FOR 211, 1-3.
  30. Donovan, G.H., Butry, D. T., The value of shade: Estimating the effect of urban trees on summertime electricity use. Energy and Buildings 41: 662–668, 2009
  31. Hashem Akbari, Sarah Bretz, Dan M. Kurn, James Hanford, Peak power and cooling energy savings of high-albedo roofs, Energy and Buildings, Volume 25, Issue 2, 1997, Pages 117-126, ISSN 0378-7788, 10.1016/S0378-7788(96)01001-8.
  32. Akbari, H. 2002. Shade trees reduce building energy use and CO2 emissions from power plants. Environmental Pollution 116: 119-126.
  33. Bourbia, F. Awbi, H.B. 2004. Building cluster and shading in urban canyon for hot dry climate Part 2: Shading simulations. Renewable Energy 29: 291–301.
  34. Chan A.L.S. 2012. Effect of adjacent shading on the thermal performance of residential buildings in a subtropical region. Applied Energy 92: 516–522.
  35. ElSherbini, A.I. Maheshwari G.P. 2010. Impact of shading air-cooled condensers on the efficiency of air-conditioning systems. Energy and Buildings 42: 1948–1951.
  36. Hien W. N. Yu C. 2004. The thermal effects of city greens on surroundings under the tropical climate. The 21th Conference on Passive and Low Energy Architecture. Eindhoven, The Netherlands, 19–22.
  37. Kumar R. Kaushik S.C. 2005. Performance evaluation of green roof and shading for thermal protection of buildings. Building and Environment 40: 1505–1511.
  38. Papadakis, G., Tsamis, P., Kyritris, S., 2001. An experimental investigation of the effect of shading with plants for solar control of buildings. Energy and Buildings 33: 831–836.
  39. Tooke T. R., Coops N. C. Voogt, J. A. Meitner M. J. 2011. Tree structure influences on rooftop-received solar radiation. Landscape and Urban Planning 102: 73–81.
  40. Raeissi, S. Taheri M. 1999. Energy saving by proper tree plantation. Building and Environment 34: 565-570.
  41. Simpson J. R. Mc Pherson E. G. 1998. Simulation of Tree Shade Impacts on Residential Energy Use for Space Conditioning In Sacramento. Atmospheric Environment 32: 69- 74.
  42. Simpson J. R. 2002. Improved estimates of tree-shade effects on residential energy use. Energy and Buildings 34: 1067–1076.
  43. Tooke T. R., Coops N. C. Voogt, J. A. Meitner M. J. 2011. Tree structure influences on rooftop-received solar radiation. Landscape and Urban Planning 102: 73–81.
  44. Timo Kuuluvainen, Timo Pukkala, Effect of crown shape and tree distribution on the spatial distribution of shade, Agricultural and Forest Meteorology, Volume 40, Issue 3, August 1987, Pages 215-231, ISSN 0168-1923, 10.1016/0168-1923(87)90060-8.
  45. online at http://www.firelandsec.com/documents/tree_growth_study.pdf
  46. Carolina da Silva Jardim, Ricardo Rüther, Isabel Tourinho Salamoni, Trajano de Souza Viana, Samuel Hilário Rebechi, Paulo José Knob, The strategic siting and the roofing area requirements of building integrated photovoltaic solar energy generators in urban areas in Brazil Energy and Buildings, Volume 40, Issue 3, 2008, Pages 365-370.
  47. Siting of Active Solar Collectors and Photovoltaic ModulesNorth Caroline Solar Center; Solar Center Information,, 2011, online at: http://ncsc.ncsu.edu/wp-content/uploads/SitingActive.pdf
  48. Guide to installing a Solar Electric System, Seattle City Lights, August, 2009 online at: http://www.seattle.gov/light/conserve/cgen/docs/SCL_ElectricSolarGuide.pdf
  49. City of Santa Barbara Solar Access Height Limitations online at: http://www.santabarbaraca.gov/NR/rdonlyres/102D3AE0-4AB4-4BBA-925C-59C00723375D/0/Solar_Access_Packet.pdf
  50. Linda Kershaw, Trees of Michigan, Lone Pine Publishing International 2006.
  51. Wilbur R. Mattoon, R.B. Miller, The Forest Service, United States, Department of Agriculture, Forest Trees of Illinois, 2nd ed., 1927.
  52. Sally S. Weeks, Harmon P. Weeks, Jr., George R. Parker, Native Trees of the Midwest, West Lafayette, Ind. Purdue University Press, c2005.