Economic Assessment of Selected Regulatory Ecosystem Services (RES) in the Elgeyo and Nyambene Watersheds Ecosystems in Kenya

Evidence of increased valuation of ecosystem services (ES) globally is significant. However, most of these studies focus on marketed subsets of ES at national and international levels. Ecosystems differ in spatial scale, biophysical and ecological structure, and functionality. This requires conducting studies at the local level to understand how, for example, the watershed ecosystem contributes to humanity locally and nationally. This study focuses on selected regulatory ecosystem services (RES) in Kenya’s catchment area ecosystems (Elgeyo and Nyambene). Field-based sampling and Landsat imagery with secondary information were used to generate biophysical and ecological data. The study used market price-based, cost-based, and unit transfer methods for RES valuation. The study estimates the total value of the six selected regulatory ecosystem services (RES) at KES 41.4 billion (US$386.7 million) and KES 14.73 billion (US$137.71 million) for Elgeyo and Nyambene, respectively. This equates to KES 1.64 million (US$15,331.19) and KES 2.72 million (US$25,375) per hectare per year. Extrapolating the study estimates to the national level, the country’s regulatory ecosystem services would range from US$18.4 billion to US$30.45 billion annually. This equates to between 16.7% and 27.7% of Kenya’s GDP in 2021, underscoring the importance of watersheds to the national economy.

Wind Turbine Optimal Preventive Maintenance Scheduling Using Fibonacci Search and Genetic Algorithm

Maintenance scheduling is essential and crucial for wind turbines (WTs) to avoid breakdowns andreduce maintenance costs. Many maintenance models have been developed for WTs’ maintenance planning, suchas corrective, preventive, and predictive maintenance. Due to communities’ dependence on WTs for electricityneeds, preventive maintenance is the most widely used method for maintenance scheduling. The downside tousing this approach is that preventive maintenance (PM) is often done in fixed intervals, which is inefficient. In thispaper, a more detailed maintenance plan for a 2 MW WT has been developed. The paper’s focus is to minimize aWT’s maintenance cost based on a WT’s reliability model. This study uses a two-layer optimization framework:Fibonacci and genetic algorithm. The first layer in the optimization method (Fibonacci) finds the optimal numberof PM required for the system. In the second layer, the optimal times for preventative maintenance and optimalcomponents to maintain have been determined to minimize maintenance costs. The Monte Carlo simulationestimates WT component failure times using their lifetime distributions from the reliability model. The estimatedfailure times are then used to determine the overall corrective and PM costs during the system’s lifetime. Finally,an optimal PM schedule is proposed for a 2 MW WT using the presented method. The method used in this papercan be expanded to a wind farm or similar engineering systems.

Optimal replacement policy of products with repair-cost threshold after the extended warranty

The reliability of the product sold under a warranty is usually maintained by the manufacturer during the warranty period.After the expiry of the warranty, however, the consumer confronts a problem about how to maintain the reliability of the product.This paper proposes, from the consumer's perspective, a replacement policy after the extended warranty, under the assumption that the product is sold under the renewable free replacement warranty(RFRW) policy in which the replacement is dependent on the repair-cost threshold. The proposed replacement policy is the replacement after the extended warranty is performed by the consumer based on the repair-cost threshold or preventive replacement(PR) age, which are decision variables. The expected cost rate model is derived from the consumer's perspective. The existence and uniqueness of the optimal solution that minimizes the expected cost rate per unit time are offered. Finally, a numerical example is presented to exemplify the proposed model.

Economic value of freshwater provisioning services of the cryosphere in the Urumqi River, Northwest China

As an important component of cryospheric provisioning services, freshwater provisioning services of the cryosphere is particularly critical to human well-being and socio-economic sustainability. It is imperative to quantitatively estimate the value of freshwater provisioning services to facilitate informed decision-making for ecosystem management and economic development. This study assessed the economic value and associated changes in benefits of freshwater provisioning services for industrial, agricultural, services and domestic water uses combining cost-based method and hydrological model in the Urumqi River during 2010–2016. The results showed that the average annual economic value of agricultural, services, domestic and industrial water uses generated from freshwater provisioning services were estimated to be 1.7, 4.4, 9.9, and 15.7 million CNY. The annual value of snowmelt provisioning services of sectorial water uses was much higher than that of glacier meltwater due to the greater contribution of snowmelt to outlet streamflow than glacier melt. The relative contributions of agricultural, services, domestic and industrial sectors to total economic value of freshwater provisioning services were 6%, 13%, 32%, and 49% respectively, depending on the meltwater supply and market prices. The benefits of freshwater provisioning services from different sectors generally increased in 2010–2016, with a significant increase in the services sector. Considering the impact of changes in freshwater supply under climate change on the assessment of cryospheric provisioning services, the results emphasize the necessity of promoting industrial structure optimization and adopting resource-efficient policies.