Flexibility in district heating and cooling systems (thermal networks in general) is an important means to cope with the intermittent generation of heat and electricity as the share of renewable energy sources (RES) increases. An important source of flexibility is the thermal energy storage present in district heating and cooling networks, found in the thermal inertia of buildings, storage units and the network itself. To unlock this flexibility and to use it effectively and efficiently, a suitable control strategy is required. In this context, this paper presents a possible definition of flexibility and its sources in a thermal network. It reviews techniques to quantify flexibility and shows the need for a more advanced control strategy; moreover, it discusses the challenges involved in developing such a control strategy. Also, the literature on advanced control in thermal networks is reviewed, by making a distinction between central, distributed and hybrid control. Finally, possible future research topics are identified based on the findings.

We studied the outcome of pneumococcal meningitis in 83 children who were admitted to a referral hospital and whose meningitis was diagnosed between 1970 and 1994. The median age of the children was 8 months. The most frequently isolated capsular serotypes and/or serogroups of Streptococcus pneumoniae were 6, 14, 18, 19, and 23. Twenty-nine children (35%) were referred by other hospitals. A mortality rate of 17% (primary referrals, 7%; secondary referrals, 35%) was observed. At discharge, 25 survivors (36%) had sequelae: hearing loss (> or = 30 dB) in 19% and neurological sequelae in 25%. During admission, the presence of coma, respiratory distress, shock, a cerebrospinal fluid (CSF) protein level of > or = 2.5 g/L, a peripheral white blood cell count of < 5 x 10(9)/L, and a serum sodium level of < 135 mmol/L were associated with mortality. Sequelae were associated with the presence of coma and a CSF glucose level of < 0.6 mmol/L. We conclude that the mortality rate of pneumococcal meningitis is lower among children than among adults. Children often die of neurological sequelae, while adults frequently die of cardiorespiratory failure due to underlying diseases. For children, coma, respiratory distress, and shock during admission were the clinical findings with the strongest predictive value for sequelae or death.

No abstract

No abstract