Energy Production in Water Distribution Networks: A PAT Design Strategy

Pump operating as turbine (PAT) is an effective source of reducing the equipment cost in small hydropower plants. However, the manufacturers provide poor information on the PAT performance thus representing a limit for its wider diffusion. Additional implementation difficulties arise under variable operating conditions, characteristic of water distribution networks (WDNs). WDNs allow to obtain widespread and globally significant amount of produced energy by exploiting the head drop due to the network pressure control strategy for leak reductions. Thus a design procedure is proposed that couples a parallel hydraulic circuit with an overall plant efficiency criteria for the market pump selection within a WDN. The proposed design method allows to identify the performance curves of the PAT that maximizes the produced energy for an assigned flow and pressure-head distribution pattern. Finally, computational fluid dynamics (CFD) is shown as a suitable alternative for performance curve assessment covering the limited number of experimental data.     

National disparities and cyclical dynamics in Italy (1892–2007): was the Mezzogiorno a sheltered economy?

The paper presents the evolution of national disparities in Italy in a cyclical perspective, comparing GDP per capita growth rates in the Centre-North and South from 1892 to 2007. The aim is to evaluate the pro-cyclical pattern of macro-area divergences and to measure, with a non-parametric analysis, the degree of the Southern regions (Mezzogiorno) dependence on the whole country. A performance indicator for national growth is used to determine whether the South can be defined as a sheltered economy. Our results show that peripheral regions as a whole had different degrees of dynamism during the period considered and that the South can be defined as unequivocally sheltered only when national policies switched from industrialization and investments into simple transfers. In other periods, including recent times, national disparities do not show pro-cyclical patterns, supporting the conclusion that the Mezzogiorno has been exposed to market conditions and its economy has not always been dependent on external factors.     

Exact likelihood computation for nonlinear DSGE models with heteroskedastic innovations

Phenomena such as the Great Moderation have increased the attention of macroeconomists towards models where shock processes are not (log-)normal. This paper studies a class of discrete-time rational expectations models where the variance of exogenous innovations is subject to stochastic regime shifts. We first show that, up to a second-order approximation using perturbation methods, regime switching in the variances has an impact only on the intercept coefficients of the decision rules. We then demonstrate how to derive the exact model likelihood for the second-order approximation of the solution when there are as many shocks as observable variables. We illustrate the applicability of the proposed solution and estimation methods in the case of a small DSGE model.     

Optimization of Osmotic Desalination Plants for Water Supply Networks

Water scarcity and the poor quality of water resources are leading to a wider diffusion of desalination plants using the Reverse Osmosis (RO) process. Unfortunately, the cost of a cubic meter of fresh water produced by an RO plants is still high and many efforts are in progress to increase the efficiency of the membranes used in osmotic plants and to limit the energy required by the process. A further reduction of the energy cost could be obtained by an optimal operation of the desalination plant so reducing the hourly energy cost, or by coupling the RO plant with an energy production plant based on direct osmosis (Pressure Retarded Osmosis PRO).The economic viability of the desalination process has been analyzed until now without accounting for the integration of the RO plant with the existing water network. This analysis is developed in the present paper with reference to a hypothetical change of water supply in a real network, where a desalination plant is used to satisfy the fresh water demand. Several scenarios will be analyzed to assess the minimum cost of fresh water production and water supply to the network, including the use of energy recovery systems, such as an integrated use of RO and PRO processes, or the regulation of pressure at the network intake by a micro hydro power plant.     

Is there a trade-off between free capital mobility,financial stability and fiscal policy flexibility in the EMU?

The recent dynamics characterizing the Eurozone economy suggest the existence of a new policy trilemma faced by its member countries. According to this policy trilemma, there is a trade-off between free capital mobility, financial stability and fiscal policy flexibility. In this paper, we analyze the foundations of such a trade-off and, based on the data for 11 Eurozone countries, present an empirical investigation on the existence of the trilemma. The results highlight the existence of the trade-off, with some differences between member countries. The existence of this trilemma in the Eurozone provides arguments for implementing centralized financial supervision together with fiscal and monetary reforms that should strengthen the currency union.     

The stability of money demand in the long-run: Italy 1861–2011

Money demand stability is a crucial issue for monetary policy efficacy, and it is particularly endangered when substantial changes occur in the monetary system. By implementing the ARDL technique, this study intends to estimate the impact of money demand determinants in Italy over a long period (1861–2011) and to investigate the stability of the estimated relations. We show that instability cannot be excluded when a standard money demand function is estimated, irrespectively of the use of M1 or M2. Then, we argue that the reason for possible instability resides in the omission of relevant variables, as we show that a fully stable demand for narrow money (M1) can be obtained from an augmented money demand function involving real exchange rate and its volatility as additional explanatory variables. These results also allow us to argue that narrower monetary aggregates should be employed in order to obtain a stable estimated relation.     

Optimal Location of Pump as Turbines (PATs) in Water Distribution Networks to Recover Energy and Reduce Leakage

Water distribution networks are high energy and low efficiency systems, where water pressure is frequently reduced by dissipation valves to limit leakage. The dissipation produced by the valves can be converted to energy production to increase the efficiency and reduce the energy impact of networks. If valves are replaced by turbines or pumps as turbines (PATs), they can both reduce pressure and produce energy. This study focuses on the optimal location of PATs within a water distribution network in order to both produce energy and reduce leakage. A new optimization model is developed consisting of several linear and non-linear constraints and a newly proposed objective function, where the turbine installation costs as well as the energy production and the economic saving due to the reduction of leakage can be accounted all together. The case study shows that the application of the mathematical model to a synthetic network ensures better results, in terms of both energy production and water saving, in comparison to other procedures.     

Was the Currency Crisis in Argentina Self-Fulfilling?

The aim of this paper is to investigate whether the 2002 crisis in Argentina was, at least to some extent, self-fulfilling. The theoretical basis we refer to is the so-called “second-generation” models. We use a Markov-switching model that allows us to empirically estimate the role played by fundamentals and/or shifts in devaluation expectations. Our results suggest that shifts in expectations have induced the crisis. However, because deteriorating fundamentals are also significant, we conclude that the collapse of the peg has been partly driven by adverse fundamentals and that abrupt shifts in devaluation expectations have forced a premature exit. JEL no. C22, D84, F31