Wood Fuel Research Articles

The impacts of different heating systems on the environment: A review

This paper presents a review of the environmental impacts of most heating systems drawing together published literature on the subject, not previously available. Here, a comparison between the different systems such as coal, wood, oil, natural gas, heat pump, geothermal and solar energy is provided in terms of their environmental impact. The most important parameters considered are the emission rate and toxicity. This places the coal-fired system as the worst among all heating systems regarding the impacts on the environment. On the other hand, renewable energy sources are the most preferred sources decreasing total emissions and air pollution. In order to make a comparison between the different systems, the emissions that must be taken into consideration are CO, CO2, NOx, SO2, PMs, N2O, CH4, volatile organic compounds, polycyclic aromatic hydrocarbons and aldehydes.

Assessment of Carbon Emission by Fuel Wood Burning at Different Altitudes in Five Districts of Uttarakhand in Western Himalaya

Fuel-wood burning is a major part of fulfilling energy requirement in rural Uttarakhand India. To analyze CO2 emission from fuel wood burning /consumption rate at the household level at different altitude villages we surveyed seventy-two (N=72) villages in five (N=5) districts in Uttarakhand. The villages were categorized into three categories based on their altitudes (I) 1000-2000mts., (II) 2001-2300 Mtr., (III) 2301- 3200 Mtr. Fuel-wood consumption was estimated by closely calculating the daily actual wood consumed at the household level in villages categorized according to altitude. In the study 351 households were surveyed, of this 28 %, were between 1000-2000mts., 55.8%, of households were sampled in villages between 2001-2300 Mtr., and 16% of households were sampled between 2301 - 3200 Mtr. respectively. The average fuel-wood consumption at households’ level in categories (I) was 11 kg/ day, in category (II) was 14.6 kg/day and in category (III) it was 17.2 kg/day. The overall average value of fuel-wood consumption in all three categories was 14.26 kg/day/ household at the state level. Twenty-nine (N=29) species are primarily being used as fuel-wood in which Litcea monopetela, Bahunia varigata, Grewia, optiva, Pirus pashia, Pinus roxburghii, Quercus leucotricophora and Myrica sapadia, Betula Utilis has a major share. Annual carbon emission from fuel-wood burning in rural areas was also estimated using the formula provided by the Intergovernmental Panel on Climate Change (IPCC 1996). The annual carbon emission values for sampled villages in five districts of Uttarakhand (rural) are (I) Almora 1081.4 MtCO2, (II) Bageshwer 479.1 Mt CO2, (III) Champawat 405.6M t CO2(IV) Pithoragarh 829.8 Mt CO2(V) Tehri Garhwal 1025.7 MtCO 2. The total CO2 emission value for all five districts was 3821.6 MtCO2 annually through fuel-wood burning.

A review on performance evaluation of solar dryer and its material for drying agricultural products

The drying process is generally carried out by burning wood and fossil fuels. However, this method is expensive and may damage the environment which has an adverse impact on climate. The world is facing the problem of shortage of fossil fuels. Some researchers did historical work on design and development of solar technology which is faster, more efficient, and hygienic and better quality of the product. Several solar dryers reviewed and enlisted the performance of dryers as per application. This paper gives an idea about the recent development in solar dryers. Some solar dryers are equipped with thermal storage to enhance the efficiency and drying rate in off-sunshine hours. To overcome the sunshine irregularity, some solar dryers have come up with solar thermal reservoirs. A comprehensive review on different dryers according to the product has been carried out, which helps in development and redesign of the solar dryer. From this paper, an idea regarding products drying likes chili, turmeric, peanut, grapes, copra and fish are presented. Which type of dryer is suitable and what kind of improvement could be possible in the future is obtained. For performance evaluation of the solar dryer, researchers used parameters like moisture reduction, moisture removal rate and different efficiencies. Solar dryer did not receive commercial utility because of high initial investment, long payback period and intermittent application. The study shows that the solar dryer not only saves fossil fuel for drying but also adds great worth to improve the product quality in terms of taste and color. It also doesn’t have any harmful effect on the environment. Solar dryer is therefore ideal to use for preservation of food in rural areas. This study may help farmers and new researchers for the design new type of solar dryer for products.

Потенціал вирощування робінії звичайної (Robinia pseudoacacia L.) на порушених землях Східної Німеччини

Проаналізовано результати модельних проектів із розведення швидкозростаючих порід дерев для виробництва відновлюваної сировини в короткому циклі у лісових насадженнях та на рекультивованих після добування бурого вугілля землях Східної Німеччини. Особливу увагу звернено на робінію звичайну, оскільки її рекомендують вирощувати на малопродуктивних і порушених землях, а не за рахунок площі корінних листяних насаджень. На дев'яти дослідних територіях Бранденбурга (Східна Німеччина) проводять випробування нових концепцій культивування робінії звичайної для енергетичного використання деревини. Розробляють шляхи мобілізації раніше невикористаних, але стабільно доступних запасів деревини робінії відповідно до "Національного плану дій щодо біомаси для Німеччини" (2009). Перевагу надають економічно обґрунтованому поводженню з наявними лісовими культурами робінії на малопродуктивних і рекультивованих землях. Встановлено придатність робінії звичайної для вирощування з метою енергетичного використання на малопродуктивних землях із невеликою кількістю опадів. Оцінено потенціал біомаси робінії звичайної у Бранденбурзі, який можна мобілізувати вирощуванням робінії в короткому плантаційному циклі. Інтенсивність росту робінії звичайної була високою вже в перший рік вирощування. Дослідження підтверджують важливість властивостей ґрунту, зокрема води, доступної рослинам, аерації ґрунту та глибини кореневмісного шару для продуктивного росту й розвитку саджанців робінії звичайної. Висока інтенсивність коренепаросткового відтворення робінії є сприятливою для її вирощування з енергетичною метою. Застосування відповідної технології лісозаготівлі для невеликих площ та невеликий річний приріст за діаметром основи робінієвого пагона (на висоті зрізання приблизно 5 см) ускладнюють технологічний процес. Для його оптимізації потрібні короткі транспортні маршрути до споживача та можливості сушіння деревини. Висока щільність деревини робінії зумовлює високу теплоту згоряння її тріски. Робінія звичайна на малопродуктивних землях в умовах низької кількості опадів має високий приріст біомаси у перші п'ять років.

Renewable energy consumption and robust globalization(s) in OECD countries: Do oil, carbon emissions and economic activity matter?

This study examines the impact of globalization(s) on renewable energy consumption in OECD countries by endogenizing per capita GDP, oil prices and per capita carbon emissions. We use robust globalization(s) as measured by the “classic”, “reconstructed” and “revisited” globalization indexes. The novel method of Machado and Silva Panel quantile regression (2019) approach is used to obtain robust findings for the renewable energy consumption-globalization nexus. The results confirm the presence of a long-run association between renewable energy consumption with globalization(s), per capita GDP, oil prices and per capita carbon emissions. The empirical results also describe that there are positive effects for per capita income, the real price of oil and carbon emissions per capita on the renewable energy consumption. In addition, a higher level of (overall, economics, social and political) classic globalization promotes renewable energy consumption, while the “reconstructed” and “revisited” economic globalization reduces the use of renewable energy consumption, and this finding is also robust to different measures of economic globalization. Moreover, the panel quantile regression reveals that renewable energy consumption increases the domestic economy in the middle (0.50) quantile group of the population through importing more advanced technology and positive spilling over markets, while the lower quantile group and the higher quantile group of the population are using non-renewable (coal, wood) energy because of the livelihood practice that is based on coal and wood (for the lower quantiles group of the population) and for the sake of speedy growth (for the higher quantiles group of the population) that worsens the environmental quality without caring for the contents of globalization.

Cultivation of the Targeted Forest Plantations

Targeted reforestation refers to ecosystems with natural and artificial energy reserves. Additional energy reserves are spent on grow-ing and harvesting, various types of forest care, forest use, and delivery of products to consumers, including energy costs for all types of preparation. The wood to be harvested must be assessed on the energy consumption required for its production. The purpose of this work was to develop a comprehensive methodology to assess the energy effect, model the process of plantation operation considering the soil type, tree species, and technical parameters of operating machines. According to the estimation results of the trunk wood energy value, it has been established that depending on the growth rate and maturity level, the target plantations are divided into two types, which should be taken into account during planting and subsequent rotation. It is shown that with regard to the technological features of machine sys-tems and the type of plantation, it is necessary to consider dimensional characteristics of the planting scheme and the technological cycle of exploiting the forest plantation. The results of mathematical modeling following the technological parameters of operating machines and all types of costs showed that the cost of the selected target species for reforestation can provide sufficient profit when optimizing the machine system operations. The principle of modular division of machines system on power, technological, and transport modules is offered, which vary in purpose, criteria of parameters optimization, and indicators of work. The obtained mathematical model and meth-odology of target planting optimization can be applied in forestry and agricultural complexes, as well as become the basis for further research in this direction.

Recycling of ash from co-incineration of waste wood and forest fuels: An overlooked challenge in a circular bioenergy system

Wood ash recycling to forests after logging residues harvest is important to ensure long-term sustainable forest management, however, it is not recycled in Sweden at the level required to compensate for current logging residue out-take. A problem in this context is wood ash contamination through co-incineration of waste wood with forest fuels, a practice driven by the political goal of a circular bioenergy system. We performed a case study of co-incineration at a typical Swedish district heating (DH) plant, which showed that the forest fuel ash alone could be recycled to forests due to high nutrient levels. Co-incineration with waste wood resulted however in such high levels of contaminants that the ash was landfilled as hazardous waste. Our assessment of the Swedish DH sector showed that wood ash contamination through co-incineration is common, and that only a minor proportion of the ash from forest fuels is recycled to the forest. It also revealed a lack of reliable data regarding ash production and management, making implementation and evaluation of effective countermeasures difficult. Practical measures to enable wood ash recycling, such as removal of waste wood from the fuel mix, incineration of separate fuels, and ash after-treatment, are hampered by technical and economic barriers. Furthermore, no comprehensive policy tools currently exist on either a national or EU level that facilitate wood ash recycling. Thus, we conclude that comprehensive and efficient policy tools are urgently needed to overcome current barriers, and stimulate large-scale recycling of wood ash for long-term sustainable forest fuel utilisation.

Co-Firing of Natural Gas with Wood Dust Experimental Test Runs

Abstract Co-Firing biomass in the form of wood dust or sawdust with natural gas is a new concept, which was performed in a specialized burner from the Riga Technical University. In order to test the burner, primary experimental test runs were performed to get an overview of flue gas behaviour. The addition of sawdust increased CO values but O2 values remained very low in the flue gases. This was due to technical problems with the fuel. Co-Firing has the potential to reduce CO2 emissions of energy production and wood dust is an abundant by-product of forestry, therefore the potential has to be explored in future research.

Harvendusraiete tasuvuse analüüs ja pikaajalise mõju simulatsioonid Järvselja õppe- ja katsemetskonnas

Abstract The results of the analysis of profitability and impact of thinning on wood production in Järvselja Training and Experimental Forest Centre are presented in the article. The profitability was assessed on the basis of harvesting income and costs of logging operations in 2015–2017. The impact of thinning on the wood production was assessed using the MOTTI simulation program. Three different scenarios for the management of the stand were compared: 1) stand management in accordance with the Finnish forest management recommendations (Tapio recommendations), 2) management according to the Estonian Forest Management Regulations and 3) stand development without thinning. The results revealed that 61 thinnings out of the 70 were profitable. The average net income from thinning was 344 euros per hectare. Fuel wood accounted for 45% and pulpwood for 30% of the harvested timber. Net present value was applied as a criterion to assess the profitability of long-term management scenarios. Considering Tapio's recommendations, the total net present value was 33% higher and following Estonian forest management rules, it was 23% higher compared to the simulations without thinning. The results indicated that thinning is economically viable in the long run. In simulations without thinning, timber production is the highest, but the net present value of management is lower compared to simulations with thinning.

A comparison of tree biometric performance of four tropical energy wood species

Four energy wood species, i.e. Weru (Albizia procera (Roxb.) Benth.), Akor (Acacia auriculiformis Benth), Pilang (Acacia leucophloea (Roxb.) Willd), and Kaliandra, (Calliandra calothyrsus Meisn.) that are suitable for substituting fossil energy in Indonesia were tested in experimental plots in Majalengka, West Java, Indonesia. In this paper, we assessed the performance of the planted species of up to 3.5 years old by measuring and analyzing the significant biometric parameters (height, diameter, volume, and biomass) of the trees growing on the plots. In each measurement, tree diameter and height were recorded. Volume and biomass were calculated by using allometric equations. The results showed that A. auriculiformis performed better than the other three species in terms of height, diameter, volume, and biomass. The performance was then followed by C. calothyrsus, A. procera, and A. leucophloea. The mean annual increment of volume and biomass of A. auriculiformis was 12.90 m3/ha/yr and 7.32 tonnes/ha/yr, respectively.

Colorimetry as a criterion for segregation of logging wastes from sustainable forest management in the Brazilian Amazon for bioenergy

Logging wastes from sustainable forest management in Amazon are promising for bioenergy; however, highly heterogeneous technological properties limit their proper application. This paper sought to study the potential of colorimetry in the segregation of logging wastes for bioenergy in Brazilian Amazon. Branches of twenty forest species were sampled at the Forest Management Area Rio Capim, Pará, Brazil. Analyses of the wood physical, chemical, energy, and colorimetric properties (CIEL∗a∗b∗ system) were performed. Our study detected relevant variations for basic density (0.525–0.895 g cm−3); energy density (10.2–18.2 GJ m−3); total extractives (1.8–17.9%); total lignin (30.2–38.1%); lightness (39–63); green/red axis (5–11); blue/yellow axis (9–23); color saturation (13–25), and hue angle (45–74). The parameters L∗, b∗, C, and h∗ presented negative relations with BD and ED. The most promising wood group (Manilkara elata and Dinizia excelsa) for bioenergy formed by principal component analysis presented darker (purplish-brown) and densest woods (0.895 and 0.891 g cm−3), in addition to greater stored energy (17.8 and 18.2 GJ m−3). Thus, this research proved that colorimetry has a high potential to segregate logging wastes for the production of chips and charcoal.

Assessing the Impacts of Land-Use Zoning Decisions on the Supply of Forest Ecosystem Services

Research Highlights: The informed decisions on land use require assessment of the impacts of these decisions on the supply of different ecosystem services. Background and Objectives: Scenario modeling can be used to provide harmonized and quantitative information on the impacts of various zoning decisions on the provision of various ecosystem services. In this study, we explored the effects of land-use zoning decisions on the provision of roundwood and energy wood, carbon stock of living tree components, berry yields, scenic beauty and recreation. Materials and Methods: Three alternative forest scenarios were formulated in terms of restrictions on forest management for already established land-use zones by the provinces in Finland. These data were integrated with the National Forest Inventory (NFI) plot data for forest dynamics modeling. Results: In Finland, 9% of the forest land was protected and 9% was under restricted forest management due to legislative decisions, forest owners’ decisions, or regional land use plans in 2016. These established zoning decisions resulted in an estimated 17% smaller roundwood and energy wood removals per year in 2016–2025 compared to the estimated wood removals in the scenario without any restrictions. The decrease in annual gross stumpage earnings was EUR 775 million per year. The carbon stock of living tree components in 2025 was 12% larger than in the scenario without any restrictions. Bilberry yield increased due to the restrictions considered in our study, while the restrictions had only a slight effect on cowberry yield at province and country levels. The restrictions increased the recreation value, particularly in Lapland, but only slightly affected scenic beauty at province and country levels. Conclusions: Scenario analyses support informed decision making and the balancing of different forest uses. Harmonized translation of restrictions and the use of standard indicators to model the impacts also support comparisons between the regions.

Experimental Modelling of a Solar Dryer for Wood Fuel in Epinal (France)

A solar dryer for wood was constructed and modelled based on the climatic condition of Epinal, France, during the summer, spring and winter seasons. The solar dryer was able to raise the temperature of the drying air by 38 °C in the spring and summer season with a global effective efficiency of 39%. Modelling of the drying of the log of wood was based on the global mass transfer coefficient and the geometric form of the log which was mostly cylindrical was considered. Validation was undertaken with the log covered with the bark. The coefficient of variations of numerical points with the experimental values given by the model was less than 5% with a mean average error and a mean relative error of 2.33% and 4.53%, respectively.

Renewable energy and wood fuel productions in the Nordic region: Can it be changed?

Along the last decades, carbon-free energy production has been a priority in the Nordic countries. The present study analyses the interactions between renewable energy (RE, entailing solar, wind, wave, hydro and municipal waste), and wood fuel (WF) production in Denmark, Finland, Norway and Sweden during the period 1960–2017. The method is based on a 2-lag vector error correction model, VECM (2), which is also used to simulate future developments. The main hypothesis assumes that a shock in RE will translate into direct and measurable effects on the WF production, and that both can be modelled co-integrated. The results of the study represent the four responses between renewable and wood fuel energy productions owing to exogenous impulses or shocks. In response to its own (renewable to renewable and wood fuel to wood fuel) positive shocks (i.e., unexpected increases), RE production decreases about 40% and stabilises. In contrast, WF production reduces by nearly 133%. In a mutual analysis of a positive shock on both RE and WF productions, the WF production decreases about 75% whereas RE production increases by about 83%. The results indicate that any unexpected shock in the WF market will result in an increase in RE production and possibly a decrease in WF production. The findings of this study expand current econometric analyses and help policymakers plan for future renewable energy requirements.

Women's experiences with mixed use of wood and gas cookstoves and fuels in rural Lambayeque, Peru

Introduction: Despite program efforts to encourage use of clean cookstoves and fuels to mitigate climate change, many communities continue to use wood-fueled open fires. Objectives: Describe experiences of participants with mixed use of cooking and fuel technologies (e.g. open fires and chimney stoves using wood and liquefied petroleum gas (LPG) stoves) in rural Lambayeque, Peru in 2018. Material and methods: Fifteen participants were interviewed using a qualitative exploratory research design. Data was collected through semi-structured interviews and analyzed using thematic content analysis. Results: Four categories emerged: decisions about acquiring cooking fuels are primarily based on cost; plastic trash is used to light wood-burning stoves; decisions to use gas over wood are based on quick food cooking time; and benefits and health problems are recognized, but mixed use of fuels persist. Conclusion: Use of both traditional wood cookstoves and plastic trash to ignite fires were used frequently because both are free or cheap. The environmental impact of cutting down trees isn't considered important, but interviewees did notice detriments to their wellbeing. Although gas stoves are used and benefits were mentioned, use of traditional stoves persists. We recommend that policy makers in Peru begin to address barriers to full adoption of new clean cooking technologies and consider governmental subsidies to meet families' spending priorities.

Bioenergy from crop residues: A regional analysis for heat and electricity applications in Ghana

The global campaign to minimise greenhouse gas emissions and reduce fossil fuel dependency has led to the consideration of crop residue as feedstock for various bioenergy technologies. In this study, the extent to which various crop residues in the ten administrative regions of Ghana can contribute to the specific heat and electricity demands of each region was assessed. The conversion of residues from 22 crops to briquettes, biomethane and bioethanol-based electricity were examined using resource modelling to determine their potential contribution to wood fuels, Liquefied Petroleum Gas (LPG) and electricity demand respectively. The results indicate that, the Eastern Region generated the highest amount of crop residues at 2.3 Mt, mainly from cassava stalks while the Greater Accra Region generated the least amount of crop residue from the ten regions at 52.3 kt. The conversion of selected crop residues to briquettes would contribute to 53.6% of the national wood fuel demand, with Eastern and Brong Ahafo Regions recording the highest individual contributions of 27.7 and 20.5% respectively. Biomethane would contribute to 11.7% of LPG demand in all the ten regions. Electricity generated from bioethanol would supplement 91.2% of the national electricity demand. Overall, the prospects are highest for the production of electricity from bioethanol produced from crop residue to support regional energy demands.

Dynamic simulation and economic analysis of a combined solar thermal and pellet heating system for domestic hot water production in a traditional Hammam

The combination of solar heating systems and low emission biomass boilers provides the opportunity to produce domestic hot water in large applications (multi-family houses, public sector, hotels, schools, etc) without the use of non-renewable energy. However, such systems are not yet widespread in Morocco, since traditional wood-fired boilers are still extensively used for water heating purposes in various applications. Therefore, the objective of this work is to evaluate the thermal performance and economic viability of a combined solar thermal and pellet heating system for hot water supply, designed for a public bathhouse under the climatic conditions of Marrakech, Morocco. Moreover, this paper presents the first small-size parabolic trough collectors installation designed for covering part of the hot water requirements in Morocco. In addition, the potential benefits of using such a system are discussed. The dynamic simulations were performed using models developed using TRNSYS 18 energy simulation software. Furthermore, we examined the effect of different system configurations on the thermal performance of the combined solar thermal and pellet heating system. The performance indicators such as solar fraction, solar system efficiency, collector efficiency and primary energy savings, are used for comparing the energy savings and the performance of these different heating systems. Besides, the life cycle cost method was carried out for the financial analysis by comparing the annual life cycle savings for the combined solar thermal and pellet heating against the conventional system (only biomass). The results presented in the current study indicate that adding solar thermal collectors to the biomass system is economically favorable. The lowest life cycle cost of the combined system was obtained with a collector area of 288 m2, which resulted in a solar fraction of 58%. In addition, an annual life-cycle savings of 5,593 € can be achieved compared to biomass boiler system taken as a reference. Moreover, up to 234 tons of CO2 emissions have been avoided through the use of the combined system. Environmentally, this system can be an attractive option for Morocco where wood energy is widely used for the production of hot water in traditional Hammams. The use of such combined solar and biomass systems may result in significant energy savings and CO2 emission reductions as well as limited deforestation in Morocco.

The Socio-economic and Bio-cultural Significances of Biodiversity Hotspots and Important Habitats in Assosa and Bambasi Woredas of Benshangul Gumuz Regional State, Ethiopia

This study was done with the aim of analyzing the socioeconomic and bio-cultural significance of biodiversity of biodiversity hotspot areas in Assosa Zone of Benishangul Gumuz Regional state of Ethiopia. Forests in Ethiopia are threatened by unsustainable uses and conversion to alternative land uses. In spite of the consequences of forest degradation and biodiversity loss and reliance of communities on forests livelihoods, there is little empirical data on the role of biodiversity in livelihoods of the local communities. This study was done in Benishangul Gumuz Regional state, in selected kebeles of Assosa and Bambasi Districts aiming to determin the Socioeconomic and biocultural uses of biodiversity to the local communities living around biodiversity hotspot areas selected. These data were obtained by interviewing 151 households. Forest product market survey was undertaken to determine prices of various forest products for valuation of forest use. Forest income was significant to households contributing 33% of total household income. Fuel wood contributed 50%, food (27%), construction material (48%), and fodder, and thatching material 51% to household forest income. Absolute forest income and relative forest income (%) were significantly different across study locations and between ethnic groups. Moreover, floral and faunal diversity was determined through transect walk along straight line in all biodiversity hotspot areas selected (Anbessa, Kolkis and Mender-42 forests). More than 118 plant species and four community types namely: Combretum molle-Croton macrostachyus (community I); Dichrostachys cinerea-Carrisa spinarum (community II); Cordia africana-Terminalia laxiflora community (Community III) and Ziziphus abyssinica- Syzygium guineense community (Community IV) were identified. Moreover, the areas are home to 20 species of mammals, over 60 species of birds, 12 species of fish, and small mammals, bats, reptiles, and amphibians. These results provide valuable information on the role of forest resources to livelihoods and could be applied in developing biodiversity conservation policies for enhanced ecosystem services and livelihoods of the study areas. Keywords : biodiversity hotspots, bicultural, biodiversity conservation, socioeconomic, floral and faunal diversity, DOI: 10.7176/JRDM/68-03 Publication date: August 31 st 2020

Exploration of membrane-based dehumidification system to improve the energy efficiency of kiln drying processes: Part 1 – Factors that affect moisture removal efficiency

Green wood drying through a steam kiln-drying technology is an energy-demanding process. This process consumes a large amount of energy to evaporate water from wood and discharge it to the atmosphere through venting. The thermal energy loss from the venting of dry kilns takes up to 20% of total energy consumed by the whole wood-drying operation because a considerably large amount of thermal energy is stored in the exhaust air. Harvesting and reusing such waster thermal energy wood improve the energy efficiency of kiln-drying process. Advanced moisture-selective membranes have been used to dehydrate humid air or gas steam because of the advantages of low energy requirements, simplicity of operation, and high specificity. However, the application of the membrane in wood-drying processes has not been addressed. Therefore, this study aimed to investigate the feasibility of using a moisture-selective membrane system to dehydrate the warm moist exhaust air to achieve an energy-saving purpose. The membrane material was polydimethylsiloxane (PDMS) with high water vapor permeability. A small membrane-based dehumidification system was constructed to evaluate the effects of four factors (temperature, airflow rate, initial RH, and vacuum pressure) on the efficiency of moisture vapor removal. Statistical analysis in terms of response surface methodology was carried out. The major findings include 1) an increase in the temperature and vacuum pressure caused a significant increase in the efficiency of moisture vapor removal, 2) the initial RH had little influence on the efficiency of moisture vapor removal, 3) increasing the airflow rate had a negative impact on the efficiency of moisture vapor removal, and 4) the regression model can be used to predict the efficiency of moisture vapor removal. This PDMS membrane would be a possible solution for a pre-drying process at relatively low operation temperatures (<45oC), that is dehumidification process.

Are shocks to disaggregated renewable energy consumption permanent or temporary for the USA? Wavelet based unit root test with smooth structural shifts

Abstract Non-stationary renewable energy consumption can be permanently affected by supply, demand and policy shocks, and in this case renewable energy promoting policies can be implemented effectively. It is therefore important to determine which type of renewable energy is stationary. To this end, we introduce a new wavelet-based unit root test which takes into account the smooth structural changes and frequency components in the series. With this method we investigate the stationary of the renewable energy consumption for the US over the period 1973m01-2019m09. To compare the results, we also use conventional ADF and wavelet-based ADF unit root tests that do not take into account structural breaks. The findings of the wavelet-based Fourier ADF unit root test indicate that biofuels energy consumption is stationary, while geothermal, waste, and wind energy consumption are non-stationary. Furthermore, the findings of the wavelet-based ADF unit root test indicate that while hydropower energy consumption is stationary at levels, solar, wood, total biomass, and total renewable energy consumption contain a unit root. Overall, we conclude that renewable energy policies implemented in the US have permanent effects on seven types of renewable energy consumption, whereas these policies have temporary effects on hydropower and biofuels energy consumption.