The operation of district heating with heat pumps and thermal energy storage in a zero-emission scenario

With the decarbonisation of electricity generation, large scale heat pumps are becoming an increasingly viable prospect for district heating installations. Heat pumps couple heat demands to an intermittent electricity supply with varying electricity prices with the use of thermal energy storage providing flexibility to avoid peak electricity charges and minimise operating costs. However, the operating strategy for cost minimising in district heating system models is dependent on the size of heat pump and thermal energy storage capacity chosen and its operational conditions. Model predictive control techniques can be used to explore district heating configurations with varying forecast horizons. This study applies optimisation to a district heating operation model simulation to find low cost combinations of heat pump and thermal energy storage sizes. Physics-based representations of a district heating network and thermal energy storage are developed with ground source heat pumps and applied to a district heat load profile with hourly marginal electricity costs derived from a modelled zero-carbon electricity system as a basis for operation. Using a dynamic programming algorithm with different forecast horizons to minimise operational costs, the total costs of combinations of heat pump and thermal energy storage sizes are calculated. The operation at smaller thermal store sizes shows cycling multiple times per day, while at larger sizes these sub-daily cycles are maintained but longer multi-day cycles become more predominant. It was found that thermal energy storage equivalent of around 1% of annual demand is sufficient to minimise operating costs and enables flexibility beyond 4 days. This has important consequences for the electricity system and can facilitate the integration of variable renewable electricity

The Interaction of Management with Botanical Composition of Irrigated Grass-Legume Pasture Mixtures in the Intermountain West USA

Beef produced on semi-arid range and milk produced in confinement are the main agricultural commodities in the semi-arid western USA. The studies reported here were undertaken to determine the suitability of irrigated pasture as an alternative to traditional beef and dairy production systems. The clipping and grazing studies were not run concurrently or within the same field, but were successive steps in selecting mixtures best-suited for rotational stocking of irrigated pastures in the Intermountain West. Summaries of productivity data have been reported elsewhere (MacAdam, 2002; MacAdam et al., 2004)

CTMC calculations of electron capture and ionization in collisions of multiply charged ions with elliptical Rydberg atoms

We have performed classical trajectory Monte Carlo (CTMC) studies of electron capture and ionization in multiply charged (Q=8) ion-Rydberg atom collisions at intermediate impact velocities. Impact parallel to the minor and to the major axis, respectively, of the initial Kepler electron ellipse has been investigated. The important role of the initial electron momentum distribution found for singly charged ion impact is strongly disminished for higher projectile charge, while the initial spatial distribution remains important for all values of Q studied.Comment: 3 pages, 5 figure

Integrating Plant Secondary Metabolites and Foraging Behavior to Enhance Animal Health in Ruminant Production Systems

Legumes and forbs contain bioactives or plant secondary compounds (PSC) with potential to enhance animal health through their antibiotic, antioxidant and immunomodulatory properties that are evident even at small dietary concentrations. In turn, ruminants can regulate their ingestion of PSC through behavioral mechanisms that allow for the efficient achievement of homeostasis. High concentrations of PSC lead to food avoidance, whereas lower content of PSC in the diet achieved through regulatory mechanisms of ingestion could promote medicinal and/or prophylactic effects in the animal and concomitant health benefits to milk and meat products. Under this context, we discuss the restructuring of rangelands and pasturelands through the strategic distribution of legume- and forb-rich patches in monotonous landscapes dominated by grasses, thus re-establishing their functionality. Such strategies can synergistically complement and provide new dimensions (prophylactic-medicinal, product quality) to the forage resources already available to livestock

The Use of Temperate Tannin Containing Forage Legumes to Improve Sustainability in Forage–Livestock Production

Greenhouse gas emissions from ruminant livestock production systems contribute significantly to the environmental footprint of agriculture. Emissions are lower for feedlot systems than for grass-based systems primarily because of the extra time required for grass-finished cattle to reach slaughter weight. In contrast, legume forages are of greater quality than grasses, which enhances intake and food conversion efficiencies, leading to improvements in production and reductions in environmental impacts compared with forage grasses. In addition, the presence of certain bioactives in legumes such as condensed tannins (CT) enhance the efficiency of energy and protein use in ruminants relative to grasses and other feeds and forages. Grazing tannin-containing legumes also reduce the incidence of bloat and improve meat quality. Synergies among nutrients and bioactives when animals graze diverse legume pastures have the potential to enhance these benefits. Thus, a diversity of legumes in feeding systems may lead to more economically, environmentally, and socially sustainable beef production than grass monocultures or feedlot rations.EEA BordenaveFil: Lagrange, Sebastian Pablo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bordenave; Argentina.Fil: MacAdam, Jennifer W. Utah State University. College of Agriculture and Applied Sciences; Estados Unidos.Fil: Villalba, Juan J. Utah State University. Quinney College of Natural Resources. Department of Wildland Resources; Estados Unidos