Low cost dispatchable heat for small scale solar thermal desalination systems (Conference Presentation)

Small scale solar thermal systems are increasingly investigated in the context of decentralized energy supply, due to favorable costs of thermal energy storage (TES) in comparison with battery storage for otherwise economical PV generation. The present study provides the computational framework and results of a one year simulation of a low-cost pilot 3kWel micro-Concentrated Solar Power (micro-CSP) plant with TES. The modeling approach is based on a dynamic representation of the solar thermal loop and a steady state model of the Organic Rankine Cycle (ORC), and is validated to experimental data from a test site (Eckerd College, St. Petersburg, Florida). The simulation results predict an annual net electricity generation of 4.08 MWh/a. Based on the simulation, optimization studies focusing on the Organic Rankine Cycle (ORC) converter of the system are presented, including a control strategy allowing for a variable pinch point in the condenser that offers an annual improvement of 14.0% in comparison to a constant condensation pinch point. Absolute electricity output is increased to 4.65 MWh/a. Improvements are due to better matching to expander performance and lower condenser fan power because of higher pinch points. A method, incorporating this control strategy, is developed to economically optimize the ORC components. The process allows for optimization of the ORC subsystem in an arbitrary environment, e.g. as part of a micro-grid to minimize Levelized electricity costs (LEC). The air-cooled condenser is identified as the driving component for the ORC optimization as its influence on overall costs and performance is of major significance. Application of the optimization process to various locations in Africa illustrates economic benefits of the system in comparison to diesel generation.

Download Full-text

Low-Cost Solar Mirror Substrates and Geometries for Solar Thermal and Photovoltaic Concentrator Applications

Solar Engineering 2001: (FORUM 2001: Solar Energy — The Power to Choose) ◽

10.1115/sed2001-102 ◽

2001 ◽

Author(s):

David N. Wells

Keyword(s):

Motion Tracking ◽

Low Cost ◽

Float Glass ◽

Solar Thermal ◽

Small Scale ◽

Solar Concentrator ◽

Hail Damage ◽

Low Profile ◽

Cylindrical Reflector ◽

Cylindrical Mirror

Abstract Two principal approaches to lowering solar concentrator costs are through improved geometry (lower profile, simpler shape), and through simplified methods to make concentrator substrates. The paper discusses issues relating to fabrication of solar concentrator mirrors from inexpensive elastically bent float glass mirrors. Protection from hail damage by a novel shock absorbing back layer is presented. New low-profile concentrator geometry is presented which utilize the low-cost mirror substrates. One new geometry uses a stationary cylindrical reflector with novel arc-motion tracking absorber that appears suitable for mid-sized thermal applications. Another uses the cylindrical mirror with an azimuth-elevation tracking mechanism appears to be suitable for small-scale applications. To get even higher concentration, some low-cost secondary designs are briefly discussed which use refractive tubes or lenses as secondary concentrating elements.

Download Full-text

Pathways and challenges for efficient solar-thermal desalination

Science Advances ◽

10.1126/sciadv.aax0763 ◽

2019 ◽

Vol 5 (7) ◽

pp. eaax0763 ◽

Cited By ~ 69

Author(s):

Zhangxin Wang ◽

Thomas Horseman ◽

Anthony P. Straub ◽

Ngai Yin Yip ◽

Deyu Li ◽

...

Keyword(s):

Energy Efficiency ◽

Performance Enhancement ◽

Low Cost ◽

Water Productivity ◽

Solar Thermal ◽

Vapor Generation ◽

Performance Limit ◽

Thermal Desalination ◽

Efficient Recovery ◽

System Designs

Solar-thermal desalination (STD) is a potentially low-cost, sustainable approach for providing high-quality fresh water in the absence of water and energy infrastructures. Despite recent efforts to advance STD by improving heat-absorbing materials and system designs, the best strategies for maximizing STD performance remain uncertain. To address this problem, we identify three major steps in distillation-based STD: (i) light-to-heat energy conversion, (ii) thermal vapor generation, and (iii) conversion of vapor to water via condensation. Using specific water productivity as a quantitative metric for energy efficiency, we show that efficient recovery of the latent heat of condensation is critical for STD performance enhancement, because solar vapor generation has already been pushed toward its performance limit. We also demonstrate that STD cannot compete with photovoltaic reverse osmosis desalination in energy efficiency. We conclude by emphasizing the importance of factors other than energy efficiency, including cost, ease of maintenance, and applicability to hypersaline waters.

Download Full-text

Tools of Transformation: Appropriate Technology in U.S. Countercultural Literature

American Studies in Scandinavia ◽

10.22439/asca.v44i2.4917 ◽

2012 ◽

Vol 44 (2) ◽

pp. 75-93

Author(s):

Peter Mortensen

Keyword(s):

Low Cost ◽

Appropriate Technology ◽

Small Scale ◽

Environmental Transformation ◽

Buckminster Fuller ◽

1960S And 1970S ◽

The 1960S ◽

Environmentally Sound ◽

User Friendly ◽

Second Wave

This essay takes its cue from second-wave ecocriticism and from recent scholarly interest in the “appropriate technology” movement that evolved during the 1960s and 1970s in California and elsewhere. “Appropriate technology” (or AT) refers to a loosely-knit group of writers, engineers and designers active in the years around 1970, and more generally to the counterculture’s promotion, development and application of technologies that were small-scale, low-cost, user-friendly, human-empowering and environmentally sound. Focusing on two roughly contemporary but now largely forgotten American texts Sidney Goldfarb’s lyric poem “Solar-Heated-Rhombic-Dodecahedron” (1969) and Gurney Norman’s novel Divine Right’s Trip (1971)—I consider how “hip” literary writers contributed to eco-technological discourse and argue for the 1960s counterculture’s relevance to present-day ecological concerns. Goldfarb’s and Norman’s texts interest me because they conceptualize iconic 1960s technologies—especially the Buckminster Fuller-inspired geodesic dome and the Volkswagen van—not as inherently alienating machines but as tools of profound individual, social and environmental transformation. Synthesizing antimodernist back-to-nature desires with modernist enthusiasm for (certain kinds of) machinery, these texts adumbrate a humanity- and modernity-centered post-wilderness model of environmentalism that resonates with the dilemmas that we face in our increasingly resource-impoverished, rapidly warming and densely populated world.

Download Full-text

Development of a simplified gas ultracleaning process: experiments in biomass residue-based fixed-bed gasification syngas

Biomass Conversion and Biorefinery ◽

10.1007/s13399-021-01680-x ◽

2021 ◽

Author(s):

Christian Frilund ◽

Esa Kurkela ◽

Ilkka Hiltunen

Keyword(s):

Activated Carbons ◽

Low Cost ◽

Fixed Bed ◽

Carbonyl Sulfide ◽

Gas Analysis ◽

Small Scale ◽

Cleaning Process ◽

Medium Temperature ◽

Gas Cleaning ◽

Adsorption Affinity

AbstractFor the realization of small-scale biomass-to-liquid (BTL) processes, low-cost syngas cleaning remains a major obstacle, and for this reason a simplified gas ultracleaning process is being developed. In this study, a low- to medium-temperature final gas cleaning process based on adsorption and organic solvent-free scrubbing methods was coupled to a pilot-scale staged fixed-bed gasification facility including hot filtration and catalytic reforming steps for extended duration gas cleaning tests for the generation of ultraclean syngas. The final gas cleaning process purified syngas from woody and agricultural biomass origin to a degree suitable for catalytic synthesis. The gas contained up to 3000 ppm of ammonia, 1300 ppm of benzene, 200 ppm of hydrogen sulfide, 10 ppm of carbonyl sulfide, and 5 ppm of hydrogen cyanide. Post-run characterization displayed that the accumulation of impurities on the Cu-based deoxygenation catalyst (TOS 105 h) did not occur, demonstrating that effective main impurity removal was achieved in the first two steps: acidic water scrubbing (AWC) and adsorption by activated carbons (AR). In the final test campaign, a comprehensive multipoint gas analysis confirmed that ammonia was fully removed by the scrubbing step, and benzene and H2S were fully removed by the subsequent activated carbon beds. The activated carbons achieved > 90% removal of up to 100 ppm of COS and 5 ppm of HCN in the syngas. These results provide insights into the adsorption affinity of activated carbons in a complex impurity matrix, which would be arduous to replicate in laboratory conditions.

Download Full-text

Modification of a Solar Thermal Collector to Promote Heat Transfer inside an Evacuated Tube Solar Thermal Absorber

Applied Sciences ◽

10.3390/app11094100 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4100

Author(s):

Rasa Supankanok ◽

Sukanpirom Sriwong ◽

Phisan Ponpo ◽

Wei Wu ◽

Walairat Chandra-ambhorn ◽

...

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Solar Thermal ◽

Heat Transfer Fluid ◽

Small Scale ◽

Medium Temperature ◽

Change Behavior ◽

Set Up ◽

Evacuated Tube ◽

Heating Medium

Evacuated-tube solar collector (ETSC) is developed to achieve high heating medium temperature. Heat transfer fluid contained inside a copper heat pipe directly affects the heating medium temperature. A 10 mol% of ethylene-glycol in water is the heat transfer fluid in this system. The purpose of this study is to modify inner structure of the evacuated tube for promoting heat transfer through aluminum fin to the copper heat pipe by inserting stainless-steel scrubbers in the evacuated tube to increase heat conduction surface area. The experiment is set up to measure the temperature of heat transfer fluid at a heat pipe tip which is a heat exchange area between heat transfer fluid and heating medium. The vapor/ liquid equilibrium (VLE) theory is applied to investigate phase change behavior of the heat transfer fluid. Mathematical model validated with 6 experimental results is set up to investigate the performance of ETSC system and evaluate the feasibility of applying the modified ETSC in small-scale industries. The results indicate that the average temperature of heat transfer fluid in a modified tube increased to 160.32 °C which is higher than a standard tube by approximately 22 °C leading to the increase in its efficiency by 34.96%.

Download Full-text

Understanding Spatial Variability of NO2 in Urban Areas Using Spatial Modelling and Data Fusion Approaches

Atmosphere ◽

10.3390/atmos12020179 ◽

2021 ◽

Vol 12 (2) ◽

pp. 179

Author(s):

Said Munir ◽

Martin Mayfield ◽

Daniel Coca

Keyword(s):

Data Fusion ◽

Spatial Variability ◽

Urban Areas ◽

Road Traffic ◽

Dispersion Model ◽

Low Cost ◽

Spatial Modelling ◽

City Centre ◽

Small Scale ◽

The City

Small-scale spatial variability in NO2 concentrations is analysed with the help of pollution maps. Maps of NO2 estimated by the Airviro dispersion model and land use regression (LUR) model are fused with measured NO2 concentrations from low-cost sensors (LCS), reference sensors and diffusion tubes. In this study, geostatistical universal kriging was employed for fusing (integrating) model estimations with measured NO2 concentrations. The results showed that the data fusion approach was capable of estimating realistic NO2 concentration maps that inherited spatial patterns of the pollutant from the model estimations and adjusted the modelled values using the measured concentrations. Maps produced by the fusion of NO2-LCS with NO2-LUR produced better results, with r-value 0.96 and RMSE 9.09. Data fusion adds value to both measured and estimated concentrations: the measured data are improved by predicting spatiotemporal gaps, whereas the modelled data are improved by constraining them with observed data. Hotspots of NO2 were shown in the city centre, eastern parts of the city towards the motorway (M1) and on some major roads. Air quality standards were exceeded at several locations in Sheffield, where annual mean NO2 levels were higher than 40 µg/m3. Road traffic was considered to be the dominant emission source of NO2 in Sheffield.

Download Full-text

A low-cost technique to measure bank erosion proces ses along middle-size river reaches

10.5194/esurf-2018-3 ◽

2018 ◽

Author(s):

Gonzalo Duró ◽

Alessandra Crosato ◽

Maarten G. Kleinhans ◽

Wim S. J. Uijttewaal

Keyword(s):

Laser Scanning ◽

Spatial Scales ◽

Low Cost ◽

Bank Erosion ◽

Water Levels ◽

Small Scale ◽

Observation Distance ◽

River Bank ◽

Erosion Processes ◽

Rtk Gps

Abstract. Diverse methods are currently available to measure river bank erosion at broad-ranging temporal and spatial scales. Yet, no technique provides low-cost and high-resolution to survey small-scale bank processes along a river reach. We investigate the capabilities of Structure-from-Motion photogrammetry applied with imagery from an Unmanned Aerial Vehicle (UAV) to describe the evolution of riverbank profiles in middle-size rivers. The bank erosion cycle is used as a reference to assess the applicability of different techniques. We surveyed 1.2 km of a restored bank of the Meuse River eight times within a year, combining different photograph perspectives and overlaps to identify an efficient UAV flight to monitor banks. The accuracy of the Digital Surface Models (DSMs) was evaluated compared with RTK GPS points and an Airborne Laser Scanning (ALS) of the whole reach. An oblique perspective with eight photo overlaps was sufficient to achieve the highest relative precision to observation distance of ~1:1400, with 10 cm error range. A complementary nadiral view increased coverage behind bank toe vegetation. The DSM and ALS had comparable accuracies except on banks, where the latter overestimates elevations. Sequential DSMs captured signatures of the erosion cycle such as mass failures, slump-block deposition, and bank undermining. Although this technique requires low water levels and banks without dense vegetation, it is a low-cost method to survey reach-scale riverbanks in sufficient resolution to quantify bank retreat and identify morphological features of the bank failure and erosion processes.

Download Full-text

Integrated Process for Textile Cotton Waste (TCW) Valorization: Waste-to-Energy and Wastewater Decontamination

Volume 6B: Energy ◽

10.1115/imece2016-66706 ◽

2016 ◽

Author(s):

A. Ribeiro ◽

C. Vilarinho ◽

J. Araújo ◽

J. Carvalho

Keyword(s):

Raw Materials ◽

Removal Rate ◽

Low Cost ◽

Calorific Value ◽

Waste To Energy ◽

Synthetic Wastewater ◽

Small Scale ◽

World Population ◽

Cotton Waste ◽

Textile Industries

The increasing of world population, industrialization and global consuming, existing market products existed in the along with diversification of raw materials, are responsible for an exponential increase of wastes. This scenario represents loss of resources and ultimately causes air, soils and water pollution. Therefore, proper waste management is currently one of the major challenges faced by modern societies. Textile industries represents, in Portugal, almost 10% of total productive transforming sector and 19% of total employments in the sector composed by almost 7.000 companies. One of the main environmental problems of textile industries is the production of significant quantities of wastes from its different processing steps. According to the Portuguese Institute of Statistics (INE) these industries produce almost 500.000 tons of wastes each year, with the textile cotton waste (TCW) being the most expressive. It was estimated that 4.000 tons of TCW are produced each year in Portugal. In this work an integrated TCW valorisation procedure was evaluated, firstly by its thermal and energetic valorisation with slow pyrolysis followed by the utilization of biochar by-product, in lead and chromium synthetic wastewater decontamination. Pyrolysis experiments were conducted in a small scale rotating pyrolysis reactor with 0.1 m3 of total capacity. Results of pyrolysis experiments showed the formation of 0,241 m3 of biogas for each kilogram of TCW. Results also demonstrated that the biogas is mostly composed by hydrogen (22%), methane (14 %), carbon monoxide (20%) and carbon dioxide (12%), which represents a total high calorific value of 12.3 MJ/Nm3. Regarding biochar, results of elemental analysis demonstrated a high percentage of carbon driving its use as low cost adsorbent. Adsorption experiments were conducted with lead and chromium synthetic wastewaters (25, 50 and 100 mg L−1) in batch vessels with controlled pH. It was evaluated the behaviour of adsorption capacity and removal rate of each metal during 120 minutes of contact time using 5, 10 and 50 g L−1 of adsorbent dosage. Results indicated high affinity of adsorbent with each tested metal with 78% of removal rate in chromium and 95% in lead experiments. This suggests that biochar from TCW pyrolysis may be appropriated to wastewaters treatment, with high contents of heavy metals and it can be an effective alternative to activated carbon.

Download Full-text