Open Access Original Research Article

Evaluation of Biogas Production through Anaerobic Digestion of Aquatic Macrophytes in a Brazilian Reservoir

R. Nagipe da Silva Paulo, A. Viana Gusmão Vieira, P. Rodrigues

Journal of Energy Research and Reviews, Page 1-14
DOI: 10.9734/jenrr/2021/v7i130180

Aquatic macrophytes are important components of aquatic habitats. However, the overgrowth of aquatic plants can cause severe problems for the management of bodies of water. As a result, these plants must be removed and disposed of as waste. However, the usage of this biomass as a substrate in biogas plants would appear to be more beneficial. The present work deals with the anaerobic digestion (AD) of macrophytes species that cause inconvenience to power generation at hydroelectric plant in Minas Gerais - Brazil. The study examines the following macrophytes species; Salvinia molest Oxycarium cubense, Eichhornia crassipes, Pistia stratiotes and Brachiaria. The experiments were carried out as stainless steel reactor with temperature, agitation and pressure control. As pre-treatment of macrophytes was used heat treatment at 120°C and pressure of 1.6 atm. The maximum methane content was 60% during 40 days digestion time, for Brachiaria of higher lignin content. The result obtained, mainly with Brachiaria demonstrates the efficiency of pre-treatment for the lignocellulosic samples.

Open Access Original Research Article

Characterisation of Wastewater and Treatment Efficiency of Biogas Plants: Effluent Discharge Quality

Martha Osei-Marfo, Michael Oteng-Peprah, Esi Awuah, Nanne de Vries

Journal of Energy Research and Reviews, Page 15-28
DOI: 10.9734/jenrr/2021/v7i130181

Aims: To characterise wastewater, assess effluent quality and treatment efficiency of 3 existing biogas plants in 3 distinct institutions in Ghana and to provide relevant data necessary to policy makers to inform decision and influence policy.

Study Design: Laboratory analyses were conducted on wastewater samples from the University of Cape Coast (UCC), Mfantsipim Senior High School (Mfantsipim) and Ankaful Maximum Security Prisons (Ankaful), between January and April 2018.

Methodology: In all, 192 wastewater samples were collected from UCC, Mfantsipim and   Ankaful for analyses. Physical, chemical and biological parameters were analysed on raw wastewater and on the effluent. Quality parameters were determined using the protocol outlined in the Standard Methods.

Results: The results showed significant differences between effluent quality from UCC, Mfantsipim and Ankaful with most of the quality parameters falling within the Ghana Environmental Protection Agency (EPA) guidelines. However, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD5), chemical oxygen demand (COD), ammonia-nitrogen (NH3-N), total coliforms (T. coli), Escherichia coli (E. coli) and Salmonella spp. (salmonella) exceeded the guideline values. The ratio between BOD5/COD was 0.5 and 0.3 for UCC and Ankaful respectively, indicating high biodegradability while Mfantsipim recorded 0.06, indicating low biodegradability. The parameters which had high treatment efficiency for the biogas plants was UCC (TSS 72.22%, total volatile solids (TVS) 78.41%, BOD5 64.22%, COD 63.56%, PO4 61.29%, T. coli 1.9 log reduction, E. coli less than 1 log reduction, salmonella 1.5 log reduction and vibrio cholerae (V. cholerae) 1 log reduction) followed by Mfantsipim (BOD5 70.45%,  COD 83.84%, NO3 79.17%, T. coli 1.6 log reduction, E. coli 5 log reduction, salmonella 1.8 log reduction and V. cholerae complete removal), while Ankaful was (TDS 57.7%, TSS 68.17%, TVS 56.33%, BOD5 82.4%, COD 81.13%, T. coli less than 1 log reduction, E. coli less than 1 log reduction, salmonella less than 1 log reduction and V. cholerae 0.96 log reduction). The rest of the parameters exhibited negative and/or low values. The performance analysis of the three biogas plants showed that UCC performs a little better than Ankaful and far better than Mfantsipim in term of treatment efficiency.

Conclusion: The performance analysis indicated that the biogas plants were under-performing which could be attributed to poor maintenance, design deficiencies, poor environmental conditions and voluminous in-put loads. These factors impact the treatment efficiency resulting in relatively poor effluent quality which could put the health of the public at great risk.

It is therefore recommended that authorities and policy makers formulate appropriate regulations aimed at addressing the potential impact of poor effluent quality discharged into the environment.

Open Access Original Research Article

Reliability Analysis of Boost Converters Connected to a Solar Panel Using a Markov Approach

Rifqi Firmansyah Muktiadji, Ali Muhammad Rushdi

Journal of Energy Research and Reviews, Page 29-42
DOI: 10.9734/jenrr/2021/v7i130182

In the past few decades, the energy shortage and global warming problems became a serious concern for humanity. To solve these problems, many countries have evolved renewable energy sources (RESs) such as solar, wind, hydro, tidal, geothermal, and biomass energy sources. Solar energy is usually harvested via a solar panel that is connected to a boost converter to supply the loads. The converter has a key role in the system, since it controls the voltage at the DC bus. If any accidental fault occurs in the converter, the solar panel cannot supply electricity to the loads. Therefore, reliability evaluation of the converter is usually warranted. In this study, reliability evaluation of boost converters connected to a solar panel is carried out using the Markov technique. This technique is widely employed to evaluate the reliability and availability of a system with fixed failure and repair rates. Using the Markov method, we found that the reliability of the typical specific converter considered is 0.9986 for and that its life expectancy or Mean-Time-To-Failure (MTTF) is .

Open Access Original Research Article

The Impact of Coolant Temperatures on Various Cycle Parameters of NH3-H2O Absorption Chiller from Solar Source

Adel Akair, Hesham Baej

Journal of Energy Research and Reviews, Page 43-50
DOI: 10.9734/jenrr/2021/v7i130183

The cycles’ structure was based on recently published technical information of low-temperatures powered Ammonia-water (NH3-H2O) absorption chiller.  The cycle was completely modeled using different components available within the refrigeration library of IPSEpro software package.  Using the model a cold-water ammonia-water absorption chiller was examined and validated in accordance to the relevant thermodynamic laws and charts. A low-grade temperature solar resource was modeled to energise the proposed model. For water-cooled cycles, the rejected heat from the absorbers and the condensers was carried out by water, at an average fixed temperature of 25°C, pumped out from ground water. The results obtained show that when the Coefficient of performance (COP), heat inputs into the generator, and cooling mass flow rates are fixed, the cycle parameters are highly affected by variation of coolant temperature. For instance when cooling water temperature decreases. Also when cooling water temperature increase, the cycle pressure, usable chilled water temperature difference and desorber outlet temperature increase whereas mass concentration and refrigeration capacity decrease. The effectiveness of the generator inlet temperature (solar source) is a factor of the largest effect to the COP. The difference was 0.1401, 27.4%. The chilled water inlet temperature (underground water) is the second largest effect to the COP. The difference between the maximum and the minimum value is 0.0865 and the relative difference is 18.9% with cooling capacity 12 kW. The influence of evaporator temperature to the COP is also minimal with only 2.2% difference. The influence of absorber temperature and condenser temperature to the COP are almost identical, the relative difference is 19.2% and 18.9% respectively.

Open Access Original Research Article

Hydropower Potential in near Future Climate over Burundi (East Africa) : A Case study of Rwegura Catchment

C´elestin Manirakiza, Lawin Agnid´e Emmanuel, Lamboni Batablinl`e, Marc Niyongendako

Journal of Energy Research and Reviews, Page 51-65
DOI: 10.9734/jenrr/2021/v7i130184

This paper assessed the near future projected hydropower potential over Rwegura catchment hosting, up to date, the biggest hydropower plant of Burundi. Observed and gridded data were considered over the period 1981